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	$242.42	8.725%	$263.5711	$263.57	$263.55	$263.60
Purchase #2	$77.47	5.633%	$81.8339	$81.83	$81.85	$81.80
Purchase #3	$118.75	4.355%	$123.9216	$123.92	$123.90	$123.90
Purchase #4	$152.93	12.295%	$171.7327	$171.73	$171.75	$171.70
Purchase #5	$16.52	13.409%	$18.7352	$18.74	$18.75	$18.70
Purchase #6	$214.89	6.641%	$229.1608	$229.16	$229.15	$229.20
Purchase #7	$166.49	9.861%	$182.9076	$182.91	$182.90	$182.90
7 purchase totals =	$989.47		$1,071.8629	$1,071.86	$1,071.85	$1,071.80