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	$53.25	7.558%	$57.2746	$57.27	$57.25	$57.30
Purchase #2	$140.80	12.874%	$158.9266	$158.93	$158.95	$158.90
Purchase #3	$96.29	4.426%	$100.5518	$100.55	$100.55	$100.60
Purchase #4	$145.96	4.808%	$152.9778	$152.98	$153.00	$153.00
Purchase #5	$71.45	7.600%	$76.8802	$76.88	$76.90	$76.90
Purchase #6	$225.72	13.478%	$256.1425	$256.14	$256.15	$256.10
Purchase #7	$237.85	5.436%	$250.7795	$250.78	$250.80	$250.80
7 purchase totals =	$971.32		$1,053.5330	$1,053.53	$1,053.60	$1,053.60