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	$167.69	10.458%	$185.227	$185.23	$185.25	$185.20
Purchase #2	$190.93	6.664%	$203.6536	$203.65	$203.65	$203.70
Purchase #3	$61.36	8.437%	$66.5369	$66.54	$66.55	$66.50
Purchase #4	$54.33	7.737%	$58.5335	$58.53	$58.55	$58.50
Purchase #5	$39.91	13.688%	$45.3729	$45.37	$45.35	$45.40
Purchase #6	$216.79	11.771%	$242.3084	$242.31	$242.30	$242.30
Purchase #7	$107.94	3.125%	$111.3131	$111.31	$111.30	$111.30
7 purchase totals =	$838.95		$912.9454	$912.94	$912.95	$912.90