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	$53.73	5.256%	$56.554	$56.55	$56.55	$56.60
Purchase #2	$162.75	10.605%	$180.0096	$180.01	$180.00	$180.00
Purchase #3	$108.44	13.452%	$123.0273	$123.03	$123.05	$123.00
Purchase #4	$82.99	8.266%	$89.85	$89.85	$89.85	$89.90
Purchase #5	$16.63	8.363%	$18.0208	$18.02	$18.00	$18.00
Purchase #6	$98.49	8.755%	$107.1128	$107.11	$107.10	$107.10
Purchase #7	$168.77	13.469%	$191.5016	$191.50	$191.50	$191.50
7 purchase totals =	$691.80		$766.0761	$766.07	$766.05	$766.10