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	$134.32	9.382%	$146.9219	$146.92	$146.90	$146.90
Purchase #2	$175.53	13.606%	$199.4126	$199.41	$199.40	$199.40
Purchase #3	$189.75	7.698%	$204.357	$204.36	$204.35	$204.40
Purchase #4	$45.50	11.705%	$50.8258	$50.83	$50.85	$50.80
Purchase #5	$38.64	9.144%	$42.1732	$42.17	$42.15	$42.20
Purchase #6	$11.59	6.187%	$12.3071	$12.31	$12.30	$12.30
Purchase #7	$131.36	8.119%	$142.0251	$142.03	$142.05	$142.00
7 purchase totals =	$726.69		$798.0227	$798.03	$798.00	$798.00