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	$187.27	5.815%	$198.1598	$198.16	$198.15	$198.20
Purchase #2	$52.90	7.182%	$56.6993	$56.70	$56.70	$56.70
Purchase #3	$113.28	11.309%	$126.0908	$126.09	$126.10	$126.10
Purchase #4	$160.39	5.222%	$168.7656	$168.77	$168.75	$168.80
Purchase #5	$148.30	10.603%	$164.0242	$164.02	$164.00	$164.00
Purchase #6	$151.83	10.103%	$167.1694	$167.17	$167.15	$167.20
Purchase #7	$142.62	3.446%	$147.5347	$147.53	$147.55	$147.50
7 purchase totals =	$956.59		$1,028.4438	$1,028.44	$1,028.40	$1,028.50