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	$201.42	4.406%	$210.2946	$210.29	$210.30	$210.30
Purchase #2	$179.59	11.511%	$200.2626	$200.26	$200.25	$200.30
Purchase #3	$113.90	4.373%	$118.8808	$118.88	$118.90	$118.90
Purchase #4	$73.40	9.852%	$80.6314	$80.63	$80.65	$80.60
Purchase #5	$77.98	13.248%	$88.3108	$88.31	$88.30	$88.30
Purchase #6	$175.28	8.530%	$190.2314	$190.23	$190.25	$190.20
Purchase #7	$180.35	6.729%	$192.4858	$192.49	$192.50	$192.50
7 purchase totals =	$1,001.92		$1,081.0974	$1,081.09	$1,081.15	$1,081.10