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	$54.42	8.753%	$59.1834	$59.18	$59.20	$59.20
Purchase #2	$205.90	13.822%	$234.3595	$234.36	$234.35	$234.40
Purchase #3	$135.32	6.710%	$144.4	$144.40	$144.40	$144.40
Purchase #4	$75.67	13.106%	$85.5873	$85.59	$85.60	$85.60
Purchase #5	$153.31	5.772%	$162.1591	$162.16	$162.15	$162.20
Purchase #6	$245.72	11.344%	$273.5945	$273.59	$273.60	$273.60
Purchase #7	$198.56	6.305%	$211.0792	$211.08	$211.10	$211.10
7 purchase totals =	$1,068.90		$1,170.3630	$1,170.36	$1,170.40	$1,170.50