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	$156.63	3.185%	$161.6187	$161.62	$161.60	$161.60
Purchase #2	$113.72	3.223%	$117.3852	$117.39	$117.40	$117.40
Purchase #3	$124.65	5.232%	$131.1717	$131.17	$131.15	$131.20
Purchase #4	$248.33	6.409%	$264.2455	$264.25	$264.25	$264.20
Purchase #5	$160.80	8.271%	$174.0998	$174.10	$174.10	$174.10
Purchase #6	$38.66	4.203%	$40.2849	$40.28	$40.30	$40.30
Purchase #7	$34.60	8.713%	$37.6147	$37.61	$37.60	$37.60
7 purchase totals =	$877.39		$926.4205	$926.42	$926.40	$926.40