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	$233.81	12.842%	$263.8359	$263.84	$263.85	$263.80
Purchase #2	$12.31	11.611%	$13.7393	$13.74	$13.75	$13.70
Purchase #3	$82.91	10.341%	$91.4837	$91.48	$91.50	$91.50
Purchase #4	$41.27	5.122%	$43.3838	$43.38	$43.40	$43.40
Purchase #5	$34.57	8.740%	$37.5914	$37.59	$37.60	$37.60
Purchase #6	$195.72	3.417%	$202.4078	$202.41	$202.40	$202.40
Purchase #7	$29.44	8.119%	$31.8302	$31.83	$31.85	$31.80
7 purchase totals =	$630.03		$684.2721	$684.27	$684.35	$684.20