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	$115.63	6.231%	$122.8349	$122.83	$122.85	$122.80
Purchase #2	$70.59	11.413%	$78.6464	$78.65	$78.65	$78.60
Purchase #3	$17.90	13.747%	$20.3607	$20.36	$20.35	$20.40
Purchase #4	$158.81	7.722%	$171.0733	$171.07	$171.05	$171.10
Purchase #5	$167.27	3.642%	$173.362	$173.36	$173.35	$173.40
Purchase #6	$125.98	12.557%	$141.7993	$141.80	$141.80	$141.80
Purchase #7	$66.44	7.641%	$71.5167	$71.52	$71.50	$71.50
7 purchase totals =	$722.62		$779.5933	$779.59	$779.55	$779.60