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	$118.76	6.812%	$126.8499	$126.85	$126.85	$126.80
Purchase #2	$125.53	12.154%	$140.7869	$140.79	$140.80	$140.80
Purchase #3	$39.39	12.666%	$44.3791	$44.38	$44.40	$44.40
Purchase #4	$141.36	6.445%	$150.4707	$150.47	$150.45	$150.50
Purchase #5	$50.93	5.722%	$53.8442	$53.84	$53.85	$53.80
Purchase #6	$141.60	10.500%	$156.468	$156.47	$156.45	$156.50
Purchase #7	$37.33	8.543%	$40.5191	$40.52	$40.50	$40.50
7 purchase totals =	$654.90		$713.3179	$713.32	$713.30	$713.30