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	$93.87	6.600%	$100.0654	$100.07	$100.05	$100.10
Purchase #2	$54.31	4.169%	$56.5742	$56.57	$56.55	$56.60
Purchase #3	$18.59	4.181%	$19.3672	$19.37	$19.35	$19.40
Purchase #4	$153.80	11.282%	$171.1517	$171.15	$171.15	$171.20
Purchase #5	$152.69	6.411%	$162.479	$162.48	$162.50	$162.50
Purchase #6	$144.37	4.229%	$150.4754	$150.48	$150.50	$150.50
Purchase #7	$204.73	4.690%	$214.3318	$214.33	$214.35	$214.30
7 purchase totals =	$822.36		$874.4447	$874.45	$874.45	$874.60