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	$212.32	5.304%	$223.5815	$223.58	$223.60	$223.60
Purchase #2	$102.25	7.865%	$110.292	$110.29	$110.30	$110.30
Purchase #3	$139.56	3.251%	$144.0971	$144.10	$144.10	$144.10
Purchase #4	$138.41	5.458%	$145.9644	$145.96	$145.95	$146.00
Purchase #5	$100.57	9.810%	$110.4359	$110.44	$110.45	$110.40
Purchase #6	$237.93	13.712%	$270.555	$270.56	$270.55	$270.60
Purchase #7	$65.69	9.452%	$71.899	$71.90	$71.90	$71.90
7 purchase totals =	$996.73		$1,076.8249	$1,076.83	$1,076.85	$1,076.90