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	$84.32	7.643%	$90.7646	$90.76	$90.75	$90.80
Purchase #2	$105.59	11.700%	$117.944	$117.94	$117.95	$117.90
Purchase #3	$57.29	13.361%	$64.9445	$64.94	$64.95	$64.90
Purchase #4	$56.76	11.569%	$63.3266	$63.33	$63.35	$63.30
Purchase #5	$79.39	7.225%	$85.1259	$85.13	$85.15	$85.10
Purchase #6	$93.48	11.405%	$104.1414	$104.14	$104.15	$104.10
Purchase #7	$216.51	7.769%	$233.3307	$233.33	$233.35	$233.30
7 purchase totals =	$693.34		$759.5777	$759.57	$759.65	$759.40