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	$133.86	12.139%	$150.1093	$150.11	$150.10	$150.10
Purchase #2	$198.35	5.197%	$208.6582	$208.66	$208.65	$208.70
Purchase #3	$109.59	7.619%	$117.9397	$117.94	$117.95	$117.90
Purchase #4	$120.25	6.306%	$127.833	$127.83	$127.85	$127.80
Purchase #5	$154.71	11.478%	$172.4676	$172.47	$172.45	$172.50
Purchase #6	$104.40	9.738%	$114.5665	$114.57	$114.55	$114.60
Purchase #7	$30.35	11.476%	$33.833	$33.83	$33.85	$33.80
7 purchase totals =	$851.51		$925.4073	$925.41	$925.40	$925.40