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	$92.81	4.521%	$97.0059	$97.01	$97.00	$97.00
Purchase #2	$31.67	5.181%	$33.3108	$33.31	$33.30	$33.30
Purchase #3	$84.25	7.483%	$90.5544	$90.55	$90.55	$90.60
Purchase #4	$94.79	7.741%	$102.1277	$102.13	$102.15	$102.10
Purchase #5	$140.91	7.735%	$151.8094	$151.81	$151.80	$151.80
Purchase #6	$171.92	10.326%	$189.6725	$189.67	$189.65	$189.70
Purchase #7	$218.25	13.201%	$247.0612	$247.06	$247.05	$247.10
7 purchase totals =	$834.60		$911.5419	$911.54	$911.50	$911.60