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	$32.56	3.302%	$33.6351	$33.64	$33.65	$33.60
Purchase #2	$81.36	8.181%	$88.0161	$88.02	$88.00	$88.00
Purchase #3	$54.60	6.830%	$58.3292	$58.33	$58.35	$58.30
Purchase #4	$208.80	6.675%	$222.7374	$222.74	$222.75	$222.70
Purchase #5	$95.77	5.288%	$100.8343	$100.83	$100.85	$100.80
Purchase #6	$37.95	11.465%	$42.301	$42.30	$42.30	$42.30
Purchase #7	$112.69	3.611%	$116.7592	$116.76	$116.75	$116.80
7 purchase totals =	$623.73		$662.6123	$662.62	$662.65	$662.50