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	$62.61	5.440%	$66.016	$66.02	$66.00	$66.00
Purchase #2	$69.30	9.637%	$75.9784	$75.98	$76.00	$76.00
Purchase #3	$132.89	6.301%	$141.2634	$141.26	$141.25	$141.30
Purchase #4	$165.80	11.621%	$185.0676	$185.07	$185.05	$185.10
Purchase #5	$98.94	12.359%	$111.168	$111.17	$111.15	$111.20
Purchase #6	$182.43	3.621%	$189.0358	$189.04	$189.05	$189.00
Purchase #7	$146.60	4.407%	$153.0607	$153.06	$153.05	$153.10
7 purchase totals =	$858.57		$921.5899	$921.60	$921.55	$921.70