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	$229.41	9.283%	$250.7061	$250.71	$250.70	$250.70
Purchase #2	$99.47	10.826%	$110.2386	$110.24	$110.25	$110.20
Purchase #3	$155.97	10.622%	$172.5371	$172.54	$172.55	$172.50
Purchase #4	$205.91	4.796%	$215.7854	$215.79	$215.80	$215.80
Purchase #5	$151.54	8.501%	$164.4224	$164.42	$164.40	$164.40
Purchase #6	$50.55	9.302%	$55.2522	$55.25	$55.25	$55.30
Purchase #7	$158.47	9.424%	$173.4042	$173.40	$173.40	$173.40
7 purchase totals =	$1,051.32		$1,142.3460	$1,142.35	$1,142.35	$1,142.30