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	$172.46	10.716%	$190.9408	$190.94	$190.95	$190.90
Purchase #2	$53.77	4.450%	$56.1628	$56.16	$56.15	$56.20
Purchase #3	$45.61	12.139%	$51.1466	$51.15	$51.15	$51.10
Purchase #4	$10.76	4.389%	$11.2323	$11.23	$11.25	$11.20
Purchase #5	$38.89	5.108%	$40.8765	$40.88	$40.90	$40.90
Purchase #6	$84.99	7.797%	$91.6167	$91.62	$91.60	$91.60
Purchase #7	$69.99	6.630%	$74.6303	$74.63	$74.65	$74.60
7 purchase totals =	$476.47		$516.6060	$516.61	$516.65	$516.50