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	$73.94	11.345%	$82.3285	$82.33	$82.35	$82.30
Purchase #2	$45.31	6.240%	$48.1373	$48.14	$48.15	$48.10
Purchase #3	$174.77	13.501%	$198.3657	$198.37	$198.35	$198.40
Purchase #4	$70.46	5.299%	$74.1937	$74.19	$74.20	$74.20
Purchase #5	$56.72	13.761%	$64.5252	$64.53	$64.55	$64.50
Purchase #6	$232.45	13.856%	$264.6583	$264.66	$264.65	$264.70
Purchase #7	$19.71	10.404%	$21.7606	$21.76	$21.75	$21.80
7 purchase totals =	$673.36		$753.9693	$753.98	$754.00	$754.00