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	$195.40	13.627%	$222.0272	$222.03	$222.05	$222.00
Purchase #2	$73.60	7.285%	$78.9618	$78.96	$78.95	$79.00
Purchase #3	$241.75	11.340%	$269.1645	$269.16	$269.15	$269.20
Purchase #4	$115.36	9.671%	$126.5165	$126.52	$126.50	$126.50
Purchase #5	$25.53	9.868%	$28.0493	$28.05	$28.05	$28.00
Purchase #6	$50.80	5.766%	$53.7291	$53.73	$53.75	$53.70
Purchase #7	$160.63	7.343%	$172.4251	$172.43	$172.45	$172.40
7 purchase totals =	$863.07		$950.8735	$950.88	$950.90	$950.80