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	$247.25	10.474%	$273.147	$273.15	$273.15	$273.10
Purchase #2	$188.30	6.347%	$200.2514	$200.25	$200.25	$200.30
Purchase #3	$86.57	8.712%	$94.112	$94.11	$94.10	$94.10
Purchase #4	$110.71	4.395%	$115.5757	$115.58	$115.60	$115.60
Purchase #5	$87.57	4.586%	$91.586	$91.59	$91.60	$91.60
Purchase #6	$111.31	7.143%	$119.2609	$119.26	$119.25	$119.30
Purchase #7	$113.83	3.158%	$117.4248	$117.42	$117.40	$117.40
7 purchase totals =	$945.54		$1,011.3578	$1,011.36	$1,011.35	$1,011.40