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	$171.94	8.658%	$186.8266	$186.83	$186.85	$186.80
Purchase #2	$21.97	13.129%	$24.8544	$24.85	$24.85	$24.90
Purchase #3	$72.85	13.593%	$82.7525	$82.75	$82.75	$82.80
Purchase #4	$173.33	11.376%	$193.048	$193.05	$193.05	$193.00
Purchase #5	$44.37	12.105%	$49.741	$49.74	$49.75	$49.70
Purchase #6	$241.33	5.304%	$254.1301	$254.13	$254.15	$254.10
Purchase #7	$248.63	10.824%	$275.5417	$275.54	$275.55	$275.50
7 purchase totals =	$974.42		$1,066.8943	$1,066.89	$1,066.95	$1,066.80