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	$190.48	5.477%	$200.9126	$200.91	$200.90	$200.90
Purchase #2	$86.43	4.490%	$90.3107	$90.31	$90.30	$90.30
Purchase #3	$189.43	11.446%	$211.1122	$211.11	$211.10	$211.10
Purchase #4	$12.60	7.166%	$13.5029	$13.50	$13.50	$13.50
Purchase #5	$35.33	11.124%	$39.2601	$39.26	$39.25	$39.30
Purchase #6	$68.86	11.766%	$76.9621	$76.96	$76.95	$77.00
Purchase #7	$148.38	7.857%	$160.0382	$160.04	$160.05	$160.00
7 purchase totals =	$731.51		$792.0988	$792.09	$792.05	$792.10