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	$198.49	12.409%	$223.1206	$223.12	$223.10	$223.10
Purchase #2	$12.78	13.375%	$14.4893	$14.49	$14.50	$14.50
Purchase #3	$11.38	6.456%	$12.1147	$12.11	$12.10	$12.10
Purchase #4	$192.69	9.396%	$210.7952	$210.80	$210.80	$210.80
Purchase #5	$183.76	8.564%	$199.4972	$199.50	$199.50	$199.50
Purchase #6	$83.91	13.796%	$95.4862	$95.49	$95.50	$95.50
Purchase #7	$238.85	12.813%	$269.4539	$269.45	$269.45	$269.50
7 purchase totals =	$921.86		$1,024.9571	$1,024.96	$1,024.95	$1,025.00