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	$90.54	6.708%	$96.6134	$96.61	$96.60	$96.60
Purchase #2	$237.88	5.805%	$251.6889	$251.69	$251.70	$251.70
Purchase #3	$106.53	5.667%	$112.5671	$112.57	$112.55	$112.60
Purchase #4	$94.57	11.290%	$105.247	$105.25	$105.25	$105.20
Purchase #5	$117.33	9.865%	$128.9046	$128.90	$128.90	$128.90
Purchase #6	$43.47	4.162%	$45.2792	$45.28	$45.30	$45.30
Purchase #7	$179.42	3.367%	$185.4611	$185.46	$185.45	$185.50
7 purchase totals =	$869.74		$925.7613	$925.76	$925.75	$925.80