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	$115.84	11.112%	$128.7121	$128.71	$128.70	$128.70
Purchase #2	$127.47	3.325%	$131.7084	$131.71	$131.70	$131.70
Purchase #3	$201.92	4.540%	$211.0872	$211.09	$211.10	$211.10
Purchase #4	$140.36	4.230%	$146.2972	$146.30	$146.30	$146.30
Purchase #5	$72.69	10.117%	$80.044	$80.04	$80.05	$80.00
Purchase #6	$32.79	9.837%	$36.0156	$36.02	$36.00	$36.00
Purchase #7	$52.76	13.262%	$59.757	$59.76	$59.75	$59.80
7 purchase totals =	$743.83		$793.6215	$793.63	$793.60	$793.60