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	$199.89	4.610%	$209.1049	$209.10	$209.10	$209.10
Purchase #2	$51.46	12.132%	$57.7031	$57.70	$57.70	$57.70
Purchase #3	$5.61	5.391%	$5.9124	$5.91	$5.90	$5.90
Purchase #4	$116.53	5.697%	$123.1687	$123.17	$123.15	$123.20
Purchase #5	$44.37	12.836%	$50.0653	$50.07	$50.05	$50.10
Purchase #6	$51.39	7.686%	$55.3398	$55.34	$55.35	$55.30
Purchase #7	$244.53	4.612%	$255.8077	$255.81	$255.80	$255.80
7 purchase totals =	$713.78		$757.1019	$757.10	$757.05	$757.10