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	$67.84	5.486%	$71.5617	$71.56	$71.55	$71.60
Purchase #2	$199.35	10.745%	$220.7702	$220.77	$220.75	$220.80
Purchase #3	$32.52	3.658%	$33.7096	$33.71	$33.70	$33.70
Purchase #4	$35.98	4.295%	$37.5253	$37.53	$37.55	$37.50
Purchase #5	$38.41	3.122%	$39.6092	$39.61	$39.60	$39.60
Purchase #6	$83.38	9.487%	$91.2903	$91.29	$91.30	$91.30
Purchase #7	$169.37	9.211%	$184.9707	$184.97	$184.95	$185.00
7 purchase totals =	$626.85		$679.4370	$679.44	$679.40	$679.50