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	$207.38	7.403%	$222.7323	$222.73	$222.75	$222.70
Purchase #2	$62.28	3.434%	$64.4187	$64.42	$64.40	$64.40
Purchase #3	$76.32	8.183%	$82.5653	$82.57	$82.55	$82.60
Purchase #4	$94.58	6.695%	$100.9121	$100.91	$100.90	$100.90
Purchase #5	$76.42	7.396%	$82.072	$82.07	$82.05	$82.10
Purchase #6	$151.56	10.730%	$167.8224	$167.82	$167.80	$167.80
Purchase #7	$54.39	11.158%	$60.4588	$60.46	$60.45	$60.50
7 purchase totals =	$722.93		$780.9816	$780.98	$780.90	$781.00