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	$165.65	13.556%	$188.1055	$188.11	$188.10	$188.10
Purchase #2	$158.74	11.240%	$176.5824	$176.58	$176.60	$176.60
Purchase #3	$47.30	11.177%	$52.5867	$52.59	$52.60	$52.60
Purchase #4	$47.31	11.815%	$52.8997	$52.90	$52.90	$52.90
Purchase #5	$169.49	13.135%	$191.7525	$191.75	$191.75	$191.80
Purchase #6	$202.68	4.464%	$211.7276	$211.73	$211.75	$211.70
Purchase #7	$215.38	3.648%	$223.2371	$223.24	$223.25	$223.20
7 purchase totals =	$1,006.55		$1,096.8915	$1,096.90	$1,096.95	$1,096.90