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	$211.33	12.588%	$237.9322	$237.93	$237.95	$237.90
Purchase #2	$57.43	9.300%	$62.771	$62.77	$62.75	$62.80
Purchase #3	$242.92	9.141%	$265.1253	$265.13	$265.15	$265.10
Purchase #4	$136.41	4.255%	$142.2142	$142.21	$142.20	$142.20
Purchase #5	$96.95	8.738%	$105.4215	$105.42	$105.40	$105.40
Purchase #6	$171.80	7.545%	$184.7623	$184.76	$184.75	$184.80
Purchase #7	$20.74	3.512%	$21.4684	$21.47	$21.45	$21.50
7 purchase totals =	$937.58		$1,019.6949	$1,019.69	$1,019.65	$1,019.70