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	$230.33	5.630%	$243.2976	$243.30	$243.30	$243.30
Purchase #2	$28.71	11.343%	$31.9666	$31.97	$31.95	$32.00
Purchase #3	$250.61	5.673%	$264.8271	$264.83	$264.85	$264.80
Purchase #4	$178.92	5.479%	$188.723	$188.72	$188.70	$188.70
Purchase #5	$40.96	3.381%	$42.3449	$42.34	$42.35	$42.30
Purchase #6	$209.45	4.649%	$219.1873	$219.19	$219.20	$219.20
Purchase #7	$106.25	6.297%	$112.9406	$112.94	$112.95	$112.90
7 purchase totals =	$1,045.23		$1,103.2871	$1,103.29	$1,103.30	$1,103.20