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	$41.30	4.395%	$43.1151	$43.12	$43.10	$43.10
Purchase #2	$228.25	3.354%	$235.9055	$235.91	$235.90	$235.90
Purchase #3	$231.97	6.680%	$247.4656	$247.47	$247.45	$247.50
Purchase #4	$188.48	4.285%	$196.5564	$196.56	$196.55	$196.60
Purchase #5	$183.96	11.562%	$205.2295	$205.23	$205.25	$205.20
Purchase #6	$61.78	3.794%	$64.1239	$64.12	$64.10	$64.10
Purchase #7	$84.51	10.103%	$93.048	$93.05	$93.05	$93.00
7 purchase totals =	$1,020.25		$1,085.4440	$1,085.46	$1,085.40	$1,085.40