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	$42.37	6.778%	$45.2418	$45.24	$45.25	$45.20
Purchase #2	$35.94	4.766%	$37.6529	$37.65	$37.65	$37.70
Purchase #3	$86.41	5.838%	$91.4546	$91.45	$91.45	$91.50
Purchase #4	$39.70	4.851%	$41.6258	$41.63	$41.65	$41.60
Purchase #5	$218.48	11.128%	$242.7925	$242.79	$242.80	$242.80
Purchase #6	$83.75	10.824%	$92.8151	$92.82	$92.80	$92.80
Purchase #7	$58.32	6.506%	$62.1143	$62.11	$62.10	$62.10
7 purchase totals =	$564.97		$613.6970	$613.69	$613.70	$613.70