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	$109.32	4.325%	$114.0481	$114.05	$114.05	$114.00
Purchase #2	$98.69	3.248%	$101.8955	$101.90	$101.90	$101.90
Purchase #3	$65.73	5.112%	$69.0901	$69.09	$69.10	$69.10
Purchase #4	$135.91	9.391%	$148.6733	$148.67	$148.65	$148.70
Purchase #5	$25.94	6.264%	$27.5649	$27.56	$27.55	$27.60
Purchase #6	$55.87	6.467%	$59.4831	$59.48	$59.50	$59.50
Purchase #7	$31.92	5.309%	$33.6146	$33.61	$33.60	$33.60
7 purchase totals =	$523.38		$554.3696	$554.36	$554.35	$554.40