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	$96.48	9.792%	$105.9273	$105.93	$105.95	$105.90
Purchase #2	$33.56	9.265%	$36.6693	$36.67	$36.65	$36.70
Purchase #3	$164.54	13.648%	$186.9964	$187.00	$187.00	$187.00
Purchase #4	$147.91	7.748%	$159.3701	$159.37	$159.35	$159.40
Purchase #5	$152.61	8.335%	$165.33	$165.33	$165.35	$165.30
Purchase #6	$75.43	3.751%	$78.2594	$78.26	$78.25	$78.30
Purchase #7	$42.60	13.483%	$48.3438	$48.34	$48.35	$48.30
7 purchase totals =	$713.13		$780.8963	$780.90	$780.90	$780.90