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	$50.69	7.718%	$54.6023	$54.60	$54.60	$54.60
Purchase #2	$189.92	3.442%	$196.457	$196.46	$196.45	$196.50
Purchase #3	$209.74	4.556%	$219.2958	$219.30	$219.30	$219.30
Purchase #4	$185.27	9.586%	$203.03	$203.03	$203.05	$203.00
Purchase #5	$70.48	11.354%	$78.4823	$78.48	$78.50	$78.50
Purchase #6	$172.94	11.484%	$192.8004	$192.80	$192.80	$192.80
Purchase #7	$54.59	7.461%	$58.663	$58.66	$58.65	$58.70
7 purchase totals =	$933.63		$1,003.3308	$1,003.33	$1,003.35	$1,003.40