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	$73.75	13.426%	$83.6517	$83.65	$83.65	$83.70
Purchase #2	$209.33	3.333%	$216.307	$216.31	$216.30	$216.30
Purchase #3	$59.53	11.225%	$66.2122	$66.21	$66.20	$66.20
Purchase #4	$113.69	11.832%	$127.1418	$127.14	$127.15	$127.10
Purchase #5	$164.31	13.550%	$186.574	$186.57	$186.55	$186.60
Purchase #6	$36.34	5.776%	$38.439	$38.44	$38.45	$38.40
Purchase #7	$231.54	5.342%	$243.9089	$243.91	$243.90	$243.90
7 purchase totals =	$888.49		$962.2346	$962.23	$962.20	$962.20