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	$43.78	4.728%	$45.8499	$45.85	$45.85	$45.80
Purchase #2	$248.88	5.430%	$262.3942	$262.39	$262.40	$262.40
Purchase #3	$143.32	10.420%	$158.2539	$158.25	$158.25	$158.30
Purchase #4	$180.80	10.674%	$200.0986	$200.10	$200.10	$200.10
Purchase #5	$26.80	6.253%	$28.4758	$28.48	$28.50	$28.50
Purchase #6	$199.33	4.545%	$208.3895	$208.39	$208.40	$208.40
Purchase #7	$43.36	5.873%	$45.9065	$45.91	$45.90	$45.90
7 purchase totals =	$886.27		$949.3684	$949.37	$949.40	$949.40