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	$246.33	8.417%	$267.0636	$267.06	$267.05	$267.10
Purchase #2	$191.42	11.459%	$213.3548	$213.35	$213.35	$213.40
Purchase #3	$71.97	12.429%	$80.9152	$80.92	$80.90	$80.90
Purchase #4	$47.69	5.686%	$50.4017	$50.40	$50.40	$50.40
Purchase #5	$189.31	3.758%	$196.4243	$196.42	$196.40	$196.40
Purchase #6	$179.94	10.132%	$198.1715	$198.17	$198.15	$198.20
Purchase #7	$58.43	13.660%	$66.4115	$66.41	$66.40	$66.40
7 purchase totals =	$985.09		$1,072.7426	$1,072.73	$1,072.65	$1,072.80