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	$156.57	12.212%	$175.6903	$175.69	$175.70	$175.70
Purchase #2	$55.26	7.315%	$59.3023	$59.30	$59.30	$59.30
Purchase #3	$150.77	9.328%	$164.8338	$164.83	$164.85	$164.80
Purchase #4	$228.58	6.417%	$243.248	$243.25	$243.25	$243.20
Purchase #5	$191.78	12.259%	$215.2903	$215.29	$215.30	$215.30
Purchase #6	$11.40	6.506%	$12.1417	$12.14	$12.15	$12.10
Purchase #7	$76.98	6.450%	$81.9452	$81.95	$81.95	$81.90
7 purchase totals =	$871.34		$952.4516	$952.45	$952.50	$952.30