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	$250.77	5.289%	$264.0332	$264.03	$264.05	$264.00
Purchase #2	$108.72	6.118%	$115.3715	$115.37	$115.35	$115.40
Purchase #3	$41.62	5.415%	$43.8737	$43.87	$43.85	$43.90
Purchase #4	$147.91	11.714%	$165.2362	$165.24	$165.25	$165.20
Purchase #5	$108.67	3.198%	$112.1453	$112.15	$112.15	$112.10
Purchase #6	$172.79	10.253%	$190.5062	$190.51	$190.50	$190.50
Purchase #7	$98.46	5.601%	$103.9747	$103.97	$103.95	$104.00
7 purchase totals =	$928.94		$995.1408	$995.14	$995.10	$995.10