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	$154.33	13.150%	$174.6244	$174.62	$174.60	$174.60
Purchase #2	$57.71	11.389%	$64.2826	$64.28	$64.30	$64.30
Purchase #3	$250.97	3.806%	$260.5219	$260.52	$260.50	$260.50
Purchase #4	$13.91	8.761%	$15.1287	$15.13	$15.15	$15.10
Purchase #5	$242.50	5.760%	$256.468	$256.47	$256.45	$256.50
Purchase #6	$186.83	13.180%	$211.4542	$211.45	$211.45	$211.50
Purchase #7	$96.70	6.633%	$103.1141	$103.11	$103.10	$103.10
7 purchase totals =	$1,002.95		$1,085.5939	$1,085.58	$1,085.55	$1,085.60