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	$122.89	7.700%	$132.3525	$132.35	$132.35	$132.40
Purchase #2	$7.29	10.133%	$8.0287	$8.03	$8.05	$8.00
Purchase #3	$140.30	11.179%	$155.9841	$155.98	$156.00	$156.00
Purchase #4	$167.46	13.129%	$189.4458	$189.45	$189.45	$189.40
Purchase #5	$69.95	5.268%	$73.635	$73.64	$73.65	$73.60
Purchase #6	$99.68	11.788%	$111.4303	$111.43	$111.45	$111.40
Purchase #7	$95.33	7.667%	$102.639	$102.64	$102.65	$102.60
7 purchase totals =	$702.90		$773.5154	$773.52	$773.60	$773.40