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	$148.50	12.353%	$166.8442	$166.84	$166.85	$166.80
Purchase #2	$18.49	11.620%	$20.6385	$20.64	$20.65	$20.60
Purchase #3	$151.46	7.302%	$162.5196	$162.52	$162.50	$162.50
Purchase #4	$108.42	8.309%	$117.4286	$117.43	$117.45	$117.40
Purchase #5	$184.63	5.231%	$194.288	$194.29	$194.30	$194.30
Purchase #6	$5.72	5.287%	$6.0224	$6.02	$6.00	$6.00
Purchase #7	$37.86	11.271%	$42.1272	$42.13	$42.15	$42.10
7 purchase totals =	$655.08		$709.8685	$709.87	$709.90	$709.70