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	$180.28	4.758%	$188.8577	$188.86	$188.85	$188.90
Purchase #2	$247.88	10.468%	$273.8281	$273.83	$273.85	$273.80
Purchase #3	$245.83	11.272%	$273.54	$273.54	$273.55	$273.50
Purchase #4	$39.71	7.234%	$42.5826	$42.58	$42.60	$42.60
Purchase #5	$43.25	6.667%	$46.1335	$46.13	$46.15	$46.10
Purchase #6	$113.59	3.417%	$117.4714	$117.47	$117.45	$117.50
Purchase #7	$107.33	3.309%	$110.8815	$110.88	$110.90	$110.90
7 purchase totals =	$977.87		$1,053.2948	$1,053.29	$1,053.35	$1,053.30