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	$231.72	11.807%	$259.0792	$259.08	$259.10	$259.10
Purchase #2	$83.28	7.194%	$89.2712	$89.27	$89.25	$89.30
Purchase #3	$140.46	5.175%	$147.7288	$147.73	$147.75	$147.70
Purchase #4	$234.37	8.255%	$253.7172	$253.72	$253.70	$253.70
Purchase #5	$26.94	5.162%	$28.3306	$28.33	$28.35	$28.30
Purchase #6	$52.73	11.774%	$58.9384	$58.94	$58.95	$58.90
Purchase #7	$244.75	9.675%	$268.4296	$268.43	$268.45	$268.40
7 purchase totals =	$1,014.25		$1,105.4950	$1,105.50	$1,105.55	$1,105.40