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	$235.99	5.137%	$248.1128	$248.11	$248.10	$248.10
Purchase #2	$238.35	13.316%	$270.0887	$270.09	$270.10	$270.10
Purchase #3	$31.32	8.214%	$33.8926	$33.89	$33.90	$33.90
Purchase #4	$147.54	11.312%	$164.2297	$164.23	$164.25	$164.20
Purchase #5	$55.60	10.800%	$61.6048	$61.60	$61.60	$61.60
Purchase #6	$107.49	10.194%	$118.4475	$118.45	$118.45	$118.40
Purchase #7	$234.79	6.871%	$250.9224	$250.92	$250.90	$250.90
7 purchase totals =	$1,051.08		$1,147.2985	$1,147.29	$1,147.30	$1,147.20