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	$239.72	12.171%	$268.8963	$268.90	$268.90	$268.90
Purchase #2	$222.41	4.368%	$232.1249	$232.12	$232.10	$232.10
Purchase #3	$46.43	5.319%	$48.8996	$48.90	$48.90	$48.90
Purchase #4	$9.54	11.362%	$10.6239	$10.62	$10.60	$10.60
Purchase #5	$129.89	8.264%	$140.6241	$140.62	$140.60	$140.60
Purchase #6	$112.49	9.760%	$123.469	$123.47	$123.45	$123.50
Purchase #7	$147.28	3.454%	$152.3671	$152.37	$152.35	$152.40
7 purchase totals =	$907.76		$977.0049	$977.00	$976.90	$977.00