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	$104.81	3.179%	$108.1419	$108.14	$108.15	$108.10
Purchase #2	$196.46	7.735%	$211.6562	$211.66	$211.65	$211.70
Purchase #3	$160.26	4.713%	$167.8131	$167.81	$167.80	$167.80
Purchase #4	$39.49	6.429%	$42.0288	$42.03	$42.05	$42.00
Purchase #5	$37.57	12.492%	$42.2632	$42.26	$42.25	$42.30
Purchase #6	$204.69	8.393%	$221.8696	$221.87	$221.85	$221.90
Purchase #7	$51.72	3.331%	$53.4428	$53.44	$53.45	$53.40
7 purchase totals =	$795.00		$847.2156	$847.21	$847.20	$847.20