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	$81.96	7.736%	$88.3004	$88.30	$88.30	$88.30
Purchase #2	$88.48	13.805%	$100.6947	$100.69	$100.70	$100.70
Purchase #3	$149.63	12.631%	$168.5298	$168.53	$168.55	$168.50
Purchase #4	$204.84	12.763%	$230.9837	$230.98	$231.00	$231.00
Purchase #5	$97.80	7.607%	$105.2396	$105.24	$105.25	$105.20
Purchase #6	$158.55	6.175%	$168.3405	$168.34	$168.35	$168.30
Purchase #7	$140.31	6.525%	$149.4652	$149.47	$149.45	$149.50
7 purchase totals =	$921.57		$1,011.5539	$1,011.55	$1,011.60	$1,011.50