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	$68.50	4.589%	$71.6435	$71.64	$71.65	$71.60
Purchase #2	$48.77	13.796%	$55.4983	$55.50	$55.50	$55.50
Purchase #3	$69.99	4.221%	$72.9443	$72.94	$72.95	$72.90
Purchase #4	$34.54	11.374%	$38.4686	$38.47	$38.45	$38.50
Purchase #5	$166.39	12.645%	$187.43	$187.43	$187.45	$187.40
Purchase #6	$211.92	4.742%	$221.9692	$221.97	$221.95	$222.00
Purchase #7	$11.55	7.519%	$12.4184	$12.42	$12.40	$12.40
7 purchase totals =	$611.66		$660.3723	$660.37	$660.35	$660.30