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	$197.63	12.713%	$222.7547	$222.75	$222.75	$222.80
Purchase #2	$205.30	11.317%	$228.5338	$228.53	$228.55	$228.50
Purchase #3	$91.45	8.301%	$99.0413	$99.04	$99.05	$99.00
Purchase #4	$138.73	8.298%	$150.2418	$150.24	$150.25	$150.20
Purchase #5	$215.52	5.304%	$226.9512	$226.95	$226.95	$227.00
Purchase #6	$49.59	12.737%	$55.9063	$55.91	$55.90	$55.90
Purchase #7	$65.75	9.281%	$71.8523	$71.85	$71.85	$71.90
7 purchase totals =	$963.97		$1,055.2814	$1,055.27	$1,055.30	$1,055.30