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	$151.82	10.148%	$167.2267	$167.23	$167.25	$167.20
Purchase #2	$218.31	11.180%	$242.7171	$242.72	$242.70	$242.70
Purchase #3	$147.98	12.858%	$167.0073	$167.01	$167.00	$167.00
Purchase #4	$37.72	4.214%	$39.3095	$39.31	$39.30	$39.30
Purchase #5	$7.41	5.539%	$7.8204	$7.82	$7.80	$7.80
Purchase #6	$80.80	7.239%	$86.6491	$86.65	$86.65	$86.60
Purchase #7	$148.25	6.807%	$158.3414	$158.34	$158.35	$158.30
7 purchase totals =	$792.29		$869.0715	$869.08	$869.05	$868.90