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	$125.82	10.611%	$139.1708	$139.17	$139.15	$139.20
Purchase #2	$158.57	5.366%	$167.0789	$167.08	$167.10	$167.10
Purchase #3	$111.99	4.187%	$116.679	$116.68	$116.70	$116.70
Purchase #4	$124.30	5.436%	$131.0569	$131.06	$131.05	$131.10
Purchase #5	$27.72	3.734%	$28.7551	$28.76	$28.75	$28.80
Purchase #6	$56.49	9.576%	$61.8995	$61.90	$61.90	$61.90
Purchase #7	$95.83	11.196%	$106.5591	$106.56	$106.55	$106.60
7 purchase totals =	$700.72		$751.1993	$751.21	$751.20	$751.40