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	$66.88	7.268%	$71.7408	$71.74	$71.75	$71.70
Purchase #2	$54.57	13.352%	$61.8562	$61.86	$61.85	$61.90
Purchase #3	$108.68	13.713%	$123.5833	$123.58	$123.60	$123.60
Purchase #4	$91.35	10.299%	$100.7581	$100.76	$100.75	$100.80
Purchase #5	$250.67	4.614%	$262.2359	$262.24	$262.25	$262.20
Purchase #6	$171.40	5.615%	$181.0241	$181.02	$181.00	$181.00
Purchase #7	$216.97	13.205%	$245.6209	$245.62	$245.60	$245.60
7 purchase totals =	$960.52		$1,046.8193	$1,046.82	$1,046.80	$1,046.80