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	$248.27	10.856%	$275.2222	$275.22	$275.20	$275.20
Purchase #2	$68.81	5.138%	$72.3455	$72.35	$72.35	$72.30
Purchase #3	$58.98	4.530%	$61.6518	$61.65	$61.65	$61.70
Purchase #4	$104.44	7.605%	$112.3827	$112.38	$112.40	$112.40
Purchase #5	$12.75	6.763%	$13.6123	$13.61	$13.60	$13.60
Purchase #6	$245.98	6.718%	$262.5049	$262.50	$262.50	$262.50
Purchase #7	$168.50	12.681%	$189.8675	$189.87	$189.85	$189.90
7 purchase totals =	$907.73		$987.5869	$987.58	$987.55	$987.60