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	$98.75	5.270%	$103.9541	$103.95	$103.95	$104.00
Purchase #2	$128.65	7.478%	$138.2704	$138.27	$138.25	$138.30
Purchase #3	$62.51	13.817%	$71.147	$71.15	$71.15	$71.10
Purchase #4	$32.66	9.377%	$35.7225	$35.72	$35.70	$35.70
Purchase #5	$23.50	12.784%	$26.5042	$26.50	$26.50	$26.50
Purchase #6	$83.43	13.253%	$94.487	$94.49	$94.50	$94.50
Purchase #7	$16.30	12.720%	$18.3734	$18.37	$18.35	$18.40
7 purchase totals =	$445.80		$488.4586	$488.45	$488.40	$488.50