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	$165.34	4.515%	$172.8051	$172.81	$172.80	$172.80
Purchase #2	$60.52	3.231%	$62.4754	$62.48	$62.50	$62.50
Purchase #3	$81.63	11.347%	$90.8926	$90.89	$90.90	$90.90
Purchase #4	$186.28	4.251%	$194.1988	$194.20	$194.20	$194.20
Purchase #5	$246.80	11.768%	$275.8434	$275.84	$275.85	$275.80
Purchase #6	$229.30	12.731%	$258.4922	$258.49	$258.50	$258.50
Purchase #7	$152.89	7.485%	$164.3338	$164.33	$164.35	$164.30
7 purchase totals =	$1,122.76		$1,219.0413	$1,219.04	$1,219.10	$1,219.00