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	$169.71	8.701%	$184.4765	$184.48	$184.50	$184.50
Purchase #2	$92.97	6.821%	$99.3115	$99.31	$99.30	$99.30
Purchase #3	$211.79	11.714%	$236.5991	$236.60	$236.60	$236.60
Purchase #4	$169.26	4.126%	$176.2437	$176.24	$176.25	$176.20
Purchase #5	$238.81	3.807%	$247.9015	$247.90	$247.90	$247.90
Purchase #6	$115.59	13.748%	$131.4813	$131.48	$131.50	$131.50
Purchase #7	$72.63	13.199%	$82.2164	$82.22	$82.20	$82.20
7 purchase totals =	$1,070.76		$1,158.2300	$1,158.23	$1,158.25	$1,158.20