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	$61.51	4.436%	$64.2386	$64.24	$64.25	$64.20
Purchase #2	$144.66	4.160%	$150.6779	$150.68	$150.70	$150.70
Purchase #3	$73.38	13.456%	$83.254	$83.25	$83.25	$83.30
Purchase #4	$246.70	13.315%	$279.5481	$279.55	$279.55	$279.50
Purchase #5	$182.67	13.862%	$207.9917	$207.99	$208.00	$208.00
Purchase #6	$107.60	3.398%	$111.2562	$111.26	$111.25	$111.30
Purchase #7	$42.61	6.318%	$45.3021	$45.30	$45.30	$45.30
7 purchase totals =	$859.13		$942.2686	$942.27	$942.30	$942.30