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	$215.89	9.616%	$236.65	$236.65	$236.65	$236.70
Purchase #2	$139.47	7.584%	$150.0474	$150.05	$150.05	$150.00
Purchase #3	$142.96	5.721%	$151.1387	$151.14	$151.15	$151.10
Purchase #4	$148.30	11.750%	$165.7253	$165.73	$165.75	$165.70
Purchase #5	$156.59	10.555%	$173.1181	$173.12	$173.10	$173.10
Purchase #6	$37.84	12.718%	$42.6525	$42.65	$42.65	$42.70
Purchase #7	$78.31	5.376%	$82.5199	$82.52	$82.50	$82.50
7 purchase totals =	$919.36		$1,001.8519	$1,001.86	$1,001.85	$1,001.80