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	$40.78	7.243%	$43.7337	$43.73	$43.75	$43.70
Purchase #2	$56.25	8.860%	$61.2338	$61.23	$61.25	$61.20
Purchase #3	$86.70	6.470%	$92.3095	$92.31	$92.30	$92.30
Purchase #4	$229.52	3.500%	$237.5532	$237.55	$237.55	$237.60
Purchase #5	$76.30	6.426%	$81.203	$81.20	$81.20	$81.20
Purchase #6	$173.40	6.749%	$185.1028	$185.10	$185.10	$185.10
Purchase #7	$210.82	10.647%	$233.266	$233.27	$233.25	$233.30
7 purchase totals =	$873.77		$934.4020	$934.39	$934.40	$934.40