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	$199.98	9.483%	$218.9441	$218.94	$218.95	$218.90
Purchase #2	$29.98	13.351%	$33.9826	$33.98	$34.00	$34.00
Purchase #3	$191.98	9.116%	$209.4809	$209.48	$209.50	$209.50
Purchase #4	$157.46	9.650%	$172.6549	$172.65	$172.65	$172.70
Purchase #5	$40.38	7.194%	$43.2849	$43.28	$43.30	$43.30
Purchase #6	$79.91	11.559%	$89.1468	$89.15	$89.15	$89.10
Purchase #7	$157.35	6.687%	$167.872	$167.87	$167.85	$167.90
7 purchase totals =	$857.04		$935.3662	$935.35	$935.40	$935.40