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	$143.73	11.577%	$160.3696	$160.37	$160.35	$160.40
Purchase #2	$246.58	9.450%	$269.8818	$269.88	$269.90	$269.90
Purchase #3	$195.36	8.817%	$212.5849	$212.58	$212.60	$212.60
Purchase #4	$206.83	7.109%	$221.5335	$221.53	$221.55	$221.50
Purchase #5	$247.31	3.455%	$255.8546	$255.85	$255.85	$255.90
Purchase #6	$224.76	11.287%	$250.1287	$250.13	$250.15	$250.10
Purchase #7	$32.64	4.685%	$34.1692	$34.17	$34.15	$34.20
7 purchase totals =	$1,297.21		$1,404.5223	$1,404.51	$1,404.55	$1,404.60