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	$241.73	6.107%	$256.4925	$256.49	$256.50	$256.50
Purchase #2	$200.98	11.414%	$223.9199	$223.92	$223.90	$223.90
Purchase #3	$65.86	7.623%	$70.8805	$70.88	$70.90	$70.90
Purchase #4	$18.64	6.445%	$19.8413	$19.84	$19.85	$19.80
Purchase #5	$206.52	5.534%	$217.9488	$217.95	$217.95	$217.90
Purchase #6	$156.46	3.640%	$162.1551	$162.16	$162.15	$162.20
Purchase #7	$150.78	3.148%	$155.5266	$155.53	$155.55	$155.50
7 purchase totals =	$1,040.97		$1,106.7647	$1,106.77	$1,106.80	$1,106.70