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	$94.65	4.762%	$99.1572	$99.16	$99.15	$99.20
Purchase #2	$107.62	5.821%	$113.8846	$113.88	$113.90	$113.90
Purchase #3	$161.55	13.804%	$183.8504	$183.85	$183.85	$183.90
Purchase #4	$6.31	9.236%	$6.8928	$6.89	$6.90	$6.90
Purchase #5	$175.65	5.515%	$185.3371	$185.34	$185.35	$185.30
Purchase #6	$96.63	7.487%	$103.8647	$103.86	$103.85	$103.90
Purchase #7	$164.90	12.655%	$185.7681	$185.77	$185.75	$185.80
7 purchase totals =	$807.31		$878.7549	$878.75	$878.75	$878.90