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	$219.51	3.476%	$227.1402	$227.14	$227.15	$227.10
Purchase #2	$176.46	3.243%	$182.1826	$182.18	$182.20	$182.20
Purchase #3	$113.77	8.625%	$123.5827	$123.58	$123.60	$123.60
Purchase #4	$211.98	9.401%	$231.9082	$231.91	$231.90	$231.90
Purchase #5	$215.73	11.445%	$240.4203	$240.42	$240.40	$240.40
Purchase #6	$88.37	12.282%	$99.2236	$99.22	$99.20	$99.20
Purchase #7	$56.48	11.281%	$62.8515	$62.85	$62.85	$62.90
7 purchase totals =	$1,082.30		$1,167.3091	$1,167.30	$1,167.30	$1,167.30