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	$89.83	13.349%	$101.8214	$101.82	$101.80	$101.80
Purchase #2	$136.62	10.779%	$151.3463	$151.35	$151.35	$151.30
Purchase #3	$154.33	11.188%	$171.5964	$171.60	$171.60	$171.60
Purchase #4	$92.68	4.492%	$96.8432	$96.84	$96.85	$96.80
Purchase #5	$75.93	8.566%	$82.4342	$82.43	$82.45	$82.40
Purchase #6	$65.69	6.811%	$70.1641	$70.16	$70.15	$70.20
Purchase #7	$25.79	11.323%	$28.7102	$28.71	$28.70	$28.70
7 purchase totals =	$640.87		$702.9158	$702.91	$702.90	$702.80