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	$38.43	7.616%	$41.3568	$41.36	$41.35	$41.40
Purchase #2	$79.83	3.485%	$82.6121	$82.61	$82.60	$82.60
Purchase #3	$78.31	4.641%	$81.9444	$81.94	$81.95	$81.90
Purchase #4	$92.33	4.414%	$96.4054	$96.41	$96.40	$96.40
Purchase #5	$247.27	8.120%	$267.3483	$267.35	$267.35	$267.30
Purchase #6	$36.31	10.286%	$40.0448	$40.04	$40.05	$40.00
Purchase #7	$137.83	6.519%	$146.8151	$146.82	$146.80	$146.80
7 purchase totals =	$710.31		$756.5269	$756.53	$756.50	$756.40