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	$158.82	9.496%	$173.9015	$173.90	$173.90	$173.90
Purchase #2	$141.27	12.846%	$159.4175	$159.42	$159.40	$159.40
Purchase #3	$105.30	8.310%	$114.0504	$114.05	$114.05	$114.10
Purchase #4	$188.28	4.252%	$196.2857	$196.29	$196.30	$196.30
Purchase #5	$97.47	4.545%	$101.9	$101.90	$101.90	$101.90
Purchase #6	$19.39	8.454%	$21.0292	$21.03	$21.05	$21.00
Purchase #7	$218.41	10.819%	$242.0398	$242.04	$242.05	$242.00
7 purchase totals =	$928.94		$1,008.6241	$1,008.63	$1,008.65	$1,008.60