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	$114.83	11.437%	$127.9631	$127.96	$127.95	$128.00
Purchase #2	$52.83	9.374%	$57.7823	$57.78	$57.80	$57.80
Purchase #3	$224.47	11.716%	$250.7689	$250.77	$250.75	$250.80
Purchase #4	$143.67	10.209%	$158.3373	$158.34	$158.35	$158.30
Purchase #5	$173.91	13.359%	$197.1426	$197.14	$197.15	$197.10
Purchase #6	$37.75	6.666%	$40.2664	$40.27	$40.25	$40.30
Purchase #7	$226.87	7.625%	$244.1688	$244.17	$244.15	$244.20
7 purchase totals =	$974.33		$1,076.4294	$1,076.43	$1,076.40	$1,076.50