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	$185.73	3.298%	$191.8554	$191.86	$191.85	$191.90
Purchase #2	$150.86	11.276%	$167.871	$167.87	$167.85	$167.90
Purchase #3	$129.31	12.834%	$145.9056	$145.91	$145.90	$145.90
Purchase #4	$37.67	5.665%	$39.804	$39.80	$39.80	$39.80
Purchase #5	$119.39	5.144%	$125.5314	$125.53	$125.55	$125.50
Purchase #6	$204.34	8.426%	$221.5577	$221.56	$221.55	$221.60
Purchase #7	$35.69	5.120%	$37.5173	$37.52	$37.50	$37.50
7 purchase totals =	$862.99		$930.0424	$930.05	$930.00	$930.10