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	$102.82	11.359%	$114.4993	$114.50	$114.50	$114.50
Purchase #2	$38.91	7.486%	$41.8228	$41.82	$41.80	$41.80
Purchase #3	$144.33	12.368%	$162.1807	$162.18	$162.20	$162.20
Purchase #4	$82.53	11.869%	$92.3255	$92.33	$92.35	$92.30
Purchase #5	$52.33	5.170%	$55.0355	$55.04	$55.05	$55.00
Purchase #6	$151.65	7.108%	$162.4293	$162.43	$162.45	$162.40
Purchase #7	$159.37	6.487%	$169.7083	$169.71	$169.70	$169.70
7 purchase totals =	$731.94		$798.0014	$798.01	$798.05	$797.90