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	$83.44	10.443%	$92.1536	$92.15	$92.15	$92.20
Purchase #2	$225.74	13.817%	$256.9305	$256.93	$256.95	$256.90
Purchase #3	$145.97	4.735%	$152.8817	$152.88	$152.90	$152.90
Purchase #4	$55.91	5.230%	$58.8341	$58.83	$58.85	$58.80
Purchase #5	$176.31	11.456%	$196.5081	$196.51	$196.50	$196.50
Purchase #6	$15.36	6.703%	$16.3896	$16.39	$16.40	$16.40
Purchase #7	$35.91	3.122%	$37.0311	$37.03	$37.05	$37.00
7 purchase totals =	$738.64		$810.7287	$810.72	$810.80	$810.70