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	$55.52	6.702%	$59.241	$59.24	$59.25	$59.20
Purchase #2	$61.52	6.658%	$65.616	$65.62	$65.60	$65.60
Purchase #3	$153.34	3.456%	$158.6394	$158.64	$158.65	$158.60
Purchase #4	$60.61	4.123%	$63.109	$63.11	$63.10	$63.10
Purchase #5	$202.77	3.183%	$209.2242	$209.22	$209.20	$209.20
Purchase #6	$233.40	13.273%	$264.3792	$264.38	$264.40	$264.40
Purchase #7	$208.38	11.162%	$231.6394	$231.64	$231.65	$231.60
7 purchase totals =	$975.54		$1,051.8482	$1,051.85	$1,051.85	$1,051.70