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	$55.51	6.642%	$59.197	$59.20	$59.20	$59.20
Purchase #2	$12.88	5.605%	$13.6019	$13.60	$13.60	$13.60
Purchase #3	$64.95	9.108%	$70.8656	$70.87	$70.85	$70.90
Purchase #4	$190.56	7.793%	$205.4103	$205.41	$205.40	$205.40
Purchase #5	$172.30	4.643%	$180.2999	$180.30	$180.30	$180.30
Purchase #6	$72.72	10.496%	$80.3527	$80.35	$80.35	$80.40
Purchase #7	$211.37	9.588%	$231.6362	$231.64	$231.65	$231.60
7 purchase totals =	$780.29		$841.3636	$841.37	$841.35	$841.40