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	$93.82	9.810%	$103.0237	$103.02	$103.00	$103.00
Purchase #2	$35.80	6.142%	$37.9988	$38.00	$38.00	$38.00
Purchase #3	$109.73	12.580%	$123.534	$123.53	$123.55	$123.50
Purchase #4	$81.33	11.555%	$90.7277	$90.73	$90.75	$90.70
Purchase #5	$77.83	6.457%	$82.8555	$82.86	$82.85	$82.90
Purchase #6	$61.87	6.871%	$66.1211	$66.12	$66.10	$66.10
Purchase #7	$154.88	11.766%	$173.1032	$173.10	$173.10	$173.10
7 purchase totals =	$615.26		$677.3640	$677.36	$677.35	$677.30