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	$62.98	10.128%	$69.3586	$69.36	$69.35	$69.40
Purchase #2	$219.32	8.164%	$237.2253	$237.23	$237.25	$237.20
Purchase #3	$30.73	6.513%	$32.7314	$32.73	$32.75	$32.70
Purchase #4	$18.43	11.362%	$20.524	$20.52	$20.50	$20.50
Purchase #5	$131.59	5.261%	$138.5129	$138.51	$138.50	$138.50
Purchase #6	$37.31	11.392%	$41.5604	$41.56	$41.55	$41.60
Purchase #7	$35.68	4.126%	$37.1522	$37.15	$37.15	$37.20
7 purchase totals =	$536.04		$577.0648	$577.06	$577.05	$577.10