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	$62.55	7.866%	$67.4702	$67.47	$67.45	$67.50
Purchase #2	$171.92	3.872%	$178.5767	$178.58	$178.60	$178.60
Purchase #3	$151.92	9.180%	$165.8663	$165.87	$165.85	$165.90
Purchase #4	$91.96	11.269%	$102.323	$102.32	$102.30	$102.30
Purchase #5	$85.90	7.626%	$92.4507	$92.45	$92.45	$92.50
Purchase #6	$167.61	12.795%	$189.0557	$189.06	$189.05	$189.10
Purchase #7	$185.54	11.402%	$206.6953	$206.70	$206.70	$206.70
7 purchase totals =	$917.40		$1,002.4379	$1,002.45	$1,002.40	$1,002.60