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	$156.43	6.433%	$166.4931	$166.49	$166.50	$166.50
Purchase #2	$181.30	5.612%	$191.4746	$191.47	$191.45	$191.50
Purchase #3	$230.34	4.496%	$240.6961	$240.70	$240.70	$240.70
Purchase #4	$160.39	8.591%	$174.1691	$174.17	$174.15	$174.20
Purchase #5	$160.33	4.346%	$167.2979	$167.30	$167.30	$167.30
Purchase #6	$141.64	4.697%	$148.2928	$148.29	$148.30	$148.30
Purchase #7	$12.41	11.455%	$13.8316	$13.83	$13.85	$13.80
7 purchase totals =	$1,042.84		$1,102.2552	$1,102.25	$1,102.25	$1,102.30