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	$155.69	11.408%	$173.4511	$173.45	$173.45	$173.50
Purchase #2	$169.76	10.434%	$187.4728	$187.47	$187.45	$187.50
Purchase #3	$98.27	3.150%	$101.3655	$101.37	$101.35	$101.40
Purchase #4	$102.49	12.408%	$115.207	$115.21	$115.20	$115.20
Purchase #5	$98.85	3.810%	$102.6162	$102.62	$102.60	$102.60
Purchase #6	$141.45	12.839%	$159.6108	$159.61	$159.60	$159.60
Purchase #7	$229.76	11.366%	$255.8745	$255.87	$255.85	$255.90
7 purchase totals =	$996.27		$1,095.5979	$1,095.60	$1,095.50	$1,095.70