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	$54.43	11.582%	$60.7341	$60.73	$60.75	$60.70
Purchase #2	$237.61	10.829%	$263.3408	$263.34	$263.35	$263.30
Purchase #3	$37.96	9.131%	$41.4261	$41.43	$41.45	$41.40
Purchase #4	$120.51	5.575%	$127.2284	$127.23	$127.25	$127.20
Purchase #5	$69.28	12.844%	$78.1783	$78.18	$78.20	$78.20
Purchase #6	$61.47	13.476%	$69.7537	$69.75	$69.75	$69.80
Purchase #7	$182.63	3.250%	$188.5655	$188.57	$188.55	$188.60
7 purchase totals =	$763.89		$829.2269	$829.23	$829.30	$829.20