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	$50.86	4.253%	$53.0231	$53.02	$53.00	$53.00
Purchase #2	$142.78	10.834%	$158.2488	$158.25	$158.25	$158.20
Purchase #3	$235.77	6.446%	$250.9677	$250.97	$250.95	$251.00
Purchase #4	$247.52	6.851%	$264.4776	$264.48	$264.50	$264.50
Purchase #5	$115.69	10.256%	$127.5552	$127.56	$127.55	$127.60
Purchase #6	$88.53	4.873%	$92.8441	$92.84	$92.85	$92.80
Purchase #7	$121.57	11.656%	$135.7402	$135.74	$135.75	$135.70
7 purchase totals =	$1,002.72		$1,082.8567	$1,082.86	$1,082.85	$1,082.80