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	$54.72	12.310%	$61.456	$61.46	$61.45	$61.50
Purchase #2	$42.53	9.320%	$46.4938	$46.49	$46.50	$46.50
Purchase #3	$211.62	8.829%	$230.3039	$230.30	$230.30	$230.30
Purchase #4	$210.78	8.802%	$229.3329	$229.33	$229.35	$229.30
Purchase #5	$21.64	4.444%	$22.6017	$22.60	$22.60	$22.60
Purchase #6	$73.78	6.172%	$78.3337	$78.33	$78.35	$78.30
Purchase #7	$141.89	5.674%	$149.9408	$149.94	$149.95	$149.90
7 purchase totals =	$756.96		$818.4628	$818.45	$818.50	$818.40