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	$47.98	9.572%	$52.5726	$52.57	$52.55	$52.60
Purchase #2	$58.55	12.159%	$65.6691	$65.67	$65.65	$65.70
Purchase #3	$201.75	13.485%	$228.956	$228.96	$228.95	$229.00
Purchase #4	$170.79	10.264%	$188.3199	$188.32	$188.30	$188.30
Purchase #5	$211.51	10.413%	$233.5345	$233.53	$233.55	$233.50
Purchase #6	$207.27	10.594%	$229.2282	$229.23	$229.25	$229.20
Purchase #7	$141.70	7.348%	$152.1121	$152.11	$152.10	$152.10
7 purchase totals =	$1,039.55		$1,150.3924	$1,150.39	$1,150.35	$1,150.40