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	$209.91	11.210%	$233.4409	$233.44	$233.45	$233.40
Purchase #2	$158.32	12.229%	$177.681	$177.68	$177.70	$177.70
Purchase #3	$39.27	7.571%	$42.2431	$42.24	$42.25	$42.20
Purchase #4	$89.76	13.353%	$101.7457	$101.75	$101.75	$101.70
Purchase #5	$183.90	6.753%	$196.3188	$196.32	$196.30	$196.30
Purchase #6	$92.36	10.187%	$101.7687	$101.77	$101.75	$101.80
Purchase #7	$39.61	7.261%	$42.4861	$42.49	$42.50	$42.50
7 purchase totals =	$813.13		$895.6843	$895.69	$895.70	$895.60