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	$175.53	9.536%	$192.2685	$192.27	$192.25	$192.30
Purchase #2	$174.39	9.700%	$191.3058	$191.31	$191.30	$191.30
Purchase #3	$63.41	11.508%	$70.7072	$70.71	$70.70	$70.70
Purchase #4	$35.28	6.284%	$37.497	$37.50	$37.50	$37.50
Purchase #5	$57.69	7.328%	$61.9175	$61.92	$61.90	$61.90
Purchase #6	$226.67	9.690%	$248.6343	$248.63	$248.65	$248.60
Purchase #7	$151.85	10.819%	$168.2787	$168.28	$168.30	$168.30
7 purchase totals =	$884.82		$970.6090	$970.62	$970.60	$970.60