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	$191.34	6.689%	$204.1387	$204.14	$204.15	$204.10
Purchase #2	$23.68	9.166%	$25.8505	$25.85	$25.85	$25.90
Purchase #3	$82.90	8.365%	$89.8346	$89.83	$89.85	$89.80
Purchase #4	$141.69	11.680%	$158.2394	$158.24	$158.25	$158.20
Purchase #5	$45.62	11.140%	$50.7021	$50.70	$50.70	$50.70
Purchase #6	$213.91	7.276%	$229.4741	$229.47	$229.45	$229.50
Purchase #7	$150.60	5.472%	$158.8408	$158.84	$158.85	$158.80
7 purchase totals =	$849.74		$917.0802	$917.07	$917.10	$917.00