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	$222.83	3.156%	$229.8625	$229.86	$229.85	$229.90
Purchase #2	$244.40	12.614%	$275.2286	$275.23	$275.25	$275.20
Purchase #3	$62.75	13.678%	$71.3329	$71.33	$71.35	$71.30
Purchase #4	$57.63	11.177%	$64.0713	$64.07	$64.05	$64.10
Purchase #5	$51.90	11.721%	$57.9832	$57.98	$58.00	$58.00
Purchase #6	$159.64	8.170%	$172.6826	$172.68	$172.70	$172.70
Purchase #7	$53.53	7.543%	$57.5678	$57.57	$57.55	$57.60
7 purchase totals =	$852.68		$928.7289	$928.72	$928.75	$928.80