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	$93.78	12.599%	$105.5953	$105.60	$105.60	$105.60
Purchase #2	$110.64	7.676%	$119.1327	$119.13	$119.15	$119.10
Purchase #3	$204.47	9.241%	$223.3651	$223.37	$223.35	$223.40
Purchase #4	$246.73	10.746%	$273.2436	$273.24	$273.25	$273.20
Purchase #5	$43.76	8.432%	$47.4498	$47.45	$47.45	$47.40
Purchase #6	$24.31	12.142%	$27.2617	$27.26	$27.25	$27.30
Purchase #7	$216.85	4.464%	$226.5302	$226.53	$226.55	$226.50
7 purchase totals =	$940.54		$1,022.5784	$1,022.58	$1,022.60	$1,022.50