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	$126.76	13.732%	$144.1667	$144.17	$144.15	$144.20
Purchase #2	$132.98	9.440%	$145.5333	$145.53	$145.55	$145.50
Purchase #3	$69.51	12.428%	$78.1487	$78.15	$78.15	$78.10
Purchase #4	$210.77	8.799%	$229.3157	$229.32	$229.30	$229.30
Purchase #5	$120.34	11.380%	$134.0347	$134.03	$134.05	$134.00
Purchase #6	$207.82	11.400%	$231.5115	$231.51	$231.50	$231.50
Purchase #7	$195.84	7.802%	$211.1194	$211.12	$211.10	$211.10
7 purchase totals =	$1,064.02		$1,173.8300	$1,173.83	$1,173.80	$1,173.70