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	$58.76	5.329%	$61.8913	$61.89	$61.90	$61.90
Purchase #2	$173.86	9.708%	$190.7383	$190.74	$190.75	$190.70
Purchase #3	$162.54	4.681%	$170.1485	$170.15	$170.15	$170.10
Purchase #4	$131.67	10.614%	$145.6455	$145.65	$145.65	$145.60
Purchase #5	$198.80	6.806%	$212.3303	$212.33	$212.35	$212.30
Purchase #6	$98.45	9.768%	$108.0666	$108.07	$108.05	$108.10
Purchase #7	$235.38	7.791%	$253.7185	$253.72	$253.70	$253.70
7 purchase totals =	$1,059.46		$1,142.5390	$1,142.55	$1,142.55	$1,142.40