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	$182.43	11.623%	$203.6338	$203.63	$203.65	$203.60
Purchase #2	$82.26	4.638%	$86.0752	$86.08	$86.10	$86.10
Purchase #3	$40.93	11.837%	$45.7749	$45.77	$45.75	$45.80
Purchase #4	$179.67	6.381%	$191.1347	$191.13	$191.15	$191.10
Purchase #5	$172.78	10.207%	$190.4157	$190.42	$190.40	$190.40
Purchase #6	$33.61	11.720%	$37.5491	$37.55	$37.55	$37.50
Purchase #7	$63.39	11.524%	$70.6951	$70.70	$70.70	$70.70
7 purchase totals =	$755.07		$825.2785	$825.28	$825.30	$825.20