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	$69.59	6.552%	$74.1495	$74.15	$74.15	$74.10
Purchase #2	$222.94	13.719%	$253.5251	$253.53	$253.55	$253.50
Purchase #3	$56.39	10.835%	$62.4999	$62.50	$62.50	$62.50
Purchase #4	$60.30	4.265%	$62.8718	$62.87	$62.85	$62.90
Purchase #5	$56.83	13.373%	$64.4299	$64.43	$64.45	$64.40
Purchase #6	$163.72	11.365%	$182.3268	$182.33	$182.35	$182.30
Purchase #7	$68.39	7.180%	$73.3004	$73.30	$73.30	$73.30
7 purchase totals =	$698.16		$773.1034	$773.11	$773.15	$773.00