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	$174.52	6.252%	$185.431	$185.43	$185.45	$185.40
Purchase #2	$33.92	11.436%	$37.7991	$37.80	$37.80	$37.80
Purchase #3	$35.64	4.677%	$37.3069	$37.31	$37.30	$37.30
Purchase #4	$47.47	4.651%	$49.6778	$49.68	$49.70	$49.70
Purchase #5	$83.82	7.153%	$89.8156	$89.82	$89.80	$89.80
Purchase #6	$31.76	10.144%	$34.9817	$34.98	$35.00	$35.00
Purchase #7	$250.94	8.503%	$272.2774	$272.28	$272.30	$272.30
7 purchase totals =	$658.07		$707.2895	$707.30	$707.35	$707.30