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	$189.94	9.657%	$208.2825	$208.28	$208.30	$208.30
Purchase #2	$131.33	12.154%	$147.2918	$147.29	$147.30	$147.30
Purchase #3	$238.33	12.495%	$268.1093	$268.11	$268.10	$268.10
Purchase #4	$137.28	10.490%	$151.6807	$151.68	$151.70	$151.70
Purchase #5	$103.73	13.435%	$117.6661	$117.67	$117.65	$117.70
Purchase #6	$72.78	12.862%	$82.141	$82.14	$82.15	$82.10
Purchase #7	$36.83	4.352%	$38.4328	$38.43	$38.45	$38.40
7 purchase totals =	$910.22		$1,013.6042	$1,013.60	$1,013.65	$1,013.60