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	$162.74	6.760%	$173.7412	$173.74	$173.75	$173.70
Purchase #2	$166.53	3.610%	$172.5417	$172.54	$172.55	$172.50
Purchase #3	$78.52	10.729%	$86.9444	$86.94	$86.95	$86.90
Purchase #4	$131.97	8.731%	$143.4923	$143.49	$143.50	$143.50
Purchase #5	$29.99	10.490%	$33.136	$33.14	$33.15	$33.10
Purchase #6	$78.89	6.618%	$84.1109	$84.11	$84.10	$84.10
Purchase #7	$207.83	4.331%	$216.8311	$216.83	$216.85	$216.80
7 purchase totals =	$856.47		$910.7976	$910.79	$910.85	$910.60