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	$175.56	12.115%	$196.8291	$196.83	$196.85	$196.80
Purchase #2	$6.85	4.210%	$7.1384	$7.14	$7.15	$7.10
Purchase #3	$28.72	10.814%	$31.8258	$31.83	$31.85	$31.80
Purchase #4	$103.36	5.373%	$108.9135	$108.91	$108.90	$108.90
Purchase #5	$247.36	5.538%	$261.0588	$261.06	$261.05	$261.10
Purchase #6	$69.85	11.534%	$77.9065	$77.91	$77.90	$77.90
Purchase #7	$161.39	13.471%	$183.1308	$183.13	$183.15	$183.10
7 purchase totals =	$793.09		$866.8029	$866.81	$866.85	$866.70