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	$80.51	6.277%	$85.5636	$85.56	$85.55	$85.60
Purchase #2	$62.78	7.383%	$67.415	$67.42	$67.40	$67.40
Purchase #3	$31.75	13.365%	$35.9934	$35.99	$36.00	$36.00
Purchase #4	$127.82	3.155%	$131.8527	$131.85	$131.85	$131.90
Purchase #5	$35.57	5.358%	$37.4758	$37.48	$37.50	$37.50
Purchase #6	$171.48	5.753%	$181.3452	$181.35	$181.35	$181.30
Purchase #7	$75.25	12.318%	$84.5193	$84.52	$84.50	$84.50
7 purchase totals =	$585.16		$624.1650	$624.17	$624.15	$624.20