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	$68.94	13.610%	$78.3227	$78.32	$78.30	$78.30
Purchase #2	$199.38	6.208%	$211.7575	$211.76	$211.75	$211.80
Purchase #3	$203.35	8.133%	$219.8885	$219.89	$219.90	$219.90
Purchase #4	$230.73	10.346%	$254.6013	$254.60	$254.60	$254.60
Purchase #5	$190.40	6.668%	$203.0959	$203.10	$203.10	$203.10
Purchase #6	$142.62	3.815%	$148.061	$148.06	$148.05	$148.10
Purchase #7	$196.39	7.826%	$211.7595	$211.76	$211.75	$211.80
7 purchase totals =	$1,231.81		$1,327.4864	$1,327.49	$1,327.45	$1,327.60