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	$148.47	11.346%	$165.3154	$165.32	$165.30	$165.30
Purchase #2	$68.62	4.847%	$71.946	$71.95	$71.95	$71.90
Purchase #3	$24.64	9.593%	$27.0037	$27.00	$27.00	$27.00
Purchase #4	$138.89	8.162%	$150.2262	$150.23	$150.25	$150.20
Purchase #5	$123.26	5.826%	$130.4411	$130.44	$130.45	$130.40
Purchase #6	$73.79	6.533%	$78.6107	$78.61	$78.60	$78.60
Purchase #7	$129.51	9.457%	$141.7578	$141.76	$141.75	$141.80
7 purchase totals =	$707.18		$765.3009	$765.31	$765.30	$765.20