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	$206.34	7.607%	$222.0363	$222.04	$222.05	$222.00
Purchase #2	$20.84	4.521%	$21.7822	$21.78	$21.80	$21.80
Purchase #3	$162.53	11.592%	$181.3705	$181.37	$181.35	$181.40
Purchase #4	$81.58	7.819%	$87.9587	$87.96	$87.95	$88.00
Purchase #5	$196.79	12.802%	$221.9831	$221.98	$222.00	$222.00
Purchase #6	$37.93	5.564%	$40.0404	$40.04	$40.05	$40.00
Purchase #7	$165.47	11.148%	$183.9166	$183.92	$183.90	$183.90
7 purchase totals =	$871.48		$959.0878	$959.09	$959.10	$959.10