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	$184.48	11.773%	$206.1988	$206.20	$206.20	$206.20
Purchase #2	$49.68	11.624%	$55.4548	$55.45	$55.45	$55.50
Purchase #3	$88.82	8.697%	$96.5447	$96.54	$96.55	$96.50
Purchase #4	$15.80	13.258%	$17.8948	$17.89	$17.90	$17.90
Purchase #5	$216.92	10.113%	$238.8571	$238.86	$238.85	$238.90
Purchase #6	$244.58	12.618%	$275.4411	$275.44	$275.45	$275.40
Purchase #7	$149.54	12.871%	$168.7873	$168.79	$168.80	$168.80
7 purchase totals =	$949.82		$1,059.1786	$1,059.17	$1,059.20	$1,059.20