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	$147.75	6.208%	$156.9223	$156.92	$156.90	$156.90
Purchase #2	$72.89	13.251%	$82.5487	$82.55	$82.55	$82.50
Purchase #3	$128.40	4.563%	$134.2589	$134.26	$134.25	$134.30
Purchase #4	$227.34	13.393%	$257.7876	$257.79	$257.80	$257.80
Purchase #5	$202.67	5.527%	$213.8716	$213.87	$213.85	$213.90
Purchase #6	$128.62	13.538%	$146.0326	$146.03	$146.05	$146.00
Purchase #7	$139.96	11.664%	$156.2849	$156.28	$156.30	$156.30
7 purchase totals =	$1,047.63		$1,147.7066	$1,147.70	$1,147.70	$1,147.70