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	$111.84	3.305%	$115.5363	$115.54	$115.55	$115.50
Purchase #2	$20.72	7.822%	$22.3407	$22.34	$22.35	$22.30
Purchase #3	$245.56	12.389%	$275.9824	$275.98	$276.00	$276.00
Purchase #4	$159.85	5.325%	$168.362	$168.36	$168.35	$168.40
Purchase #5	$239.87	13.412%	$272.0414	$272.04	$272.05	$272.00
Purchase #6	$82.25	9.259%	$89.8655	$89.87	$89.85	$89.90
Purchase #7	$219.75	4.559%	$229.7684	$229.77	$229.75	$229.80
7 purchase totals =	$1,079.84		$1,173.8967	$1,173.90	$1,173.90	$1,173.90