Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.30	11.403%	$171.8948	$171.89	$171.90	$171.90
Purchase #2	$221.97	8.361%	$240.5289	$240.53	$240.55	$240.50
Purchase #3	$107.75	8.827%	$117.2611	$117.26	$117.25	$117.30
Purchase #4	$174.60	12.495%	$196.4163	$196.42	$196.40	$196.40
Purchase #5	$215.76	11.710%	$241.0255	$241.03	$241.05	$241.00
Purchase #6	$248.64	8.640%	$270.1225	$270.12	$270.10	$270.10
Purchase #7	$133.77	13.233%	$151.4718	$151.47	$151.45	$151.50
7 purchase totals =	$1,256.79		$1,388.7209	$1,388.72	$1,388.70	$1,388.70