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	$63.51	12.737%	$71.5993	$71.60	$71.60	$71.60
Purchase #2	$151.61	3.519%	$156.9452	$156.95	$156.95	$156.90
Purchase #3	$26.98	9.467%	$29.5342	$29.53	$29.55	$29.50
Purchase #4	$172.71	7.336%	$185.38	$185.38	$185.40	$185.40
Purchase #5	$200.33	4.760%	$209.8657	$209.87	$209.85	$209.90
Purchase #6	$212.68	11.449%	$237.0297	$237.03	$237.05	$237.00
Purchase #7	$90.90	5.711%	$96.0913	$96.09	$96.10	$96.10
7 purchase totals =	$918.72		$986.4454	$986.45	$986.50	$986.40