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	$93.27	3.799%	$96.8133	$96.81	$96.80	$96.80
Purchase #2	$137.97	7.593%	$148.4461	$148.45	$148.45	$148.40
Purchase #3	$150.56	13.190%	$170.4189	$170.42	$170.40	$170.40
Purchase #4	$37.83	11.174%	$42.0571	$42.06	$42.05	$42.10
Purchase #5	$169.86	9.435%	$185.8863	$185.89	$185.90	$185.90
Purchase #6	$154.35	8.360%	$167.2537	$167.25	$167.25	$167.30
Purchase #7	$216.96	3.512%	$224.5796	$224.58	$224.60	$224.60
7 purchase totals =	$960.80		$1,035.4550	$1,035.46	$1,035.45	$1,035.50