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	$69.45	5.471%	$73.2496	$73.25	$73.25	$73.20
Purchase #2	$93.69	9.114%	$102.2289	$102.23	$102.25	$102.20
Purchase #3	$246.30	8.475%	$267.1739	$267.17	$267.15	$267.20
Purchase #4	$89.50	12.427%	$100.6222	$100.62	$100.60	$100.60
Purchase #5	$20.78	3.872%	$21.5846	$21.58	$21.60	$21.60
Purchase #6	$211.44	4.765%	$221.5151	$221.52	$221.50	$221.50
Purchase #7	$130.43	12.290%	$146.4598	$146.46	$146.45	$146.50
7 purchase totals =	$861.59		$932.8341	$932.83	$932.80	$932.80