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	$157.30	9.281%	$171.899	$171.90	$171.90	$171.90
Purchase #2	$37.63	12.455%	$42.3168	$42.32	$42.30	$42.30
Purchase #3	$38.96	9.357%	$42.6055	$42.61	$42.60	$42.60
Purchase #4	$159.69	7.363%	$171.448	$171.45	$171.45	$171.40
Purchase #5	$167.62	3.725%	$173.8638	$173.86	$173.85	$173.90
Purchase #6	$240.96	6.721%	$257.1549	$257.15	$257.15	$257.20
Purchase #7	$226.53	11.133%	$251.7496	$251.75	$251.75	$251.70
7 purchase totals =	$1,028.69		$1,111.0376	$1,111.04	$1,111.00	$1,111.00