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	$40.36	12.512%	$45.4098	$45.41	$45.40	$45.40
Purchase #2	$206.44	4.163%	$215.0341	$215.03	$215.05	$215.00
Purchase #3	$93.32	10.552%	$103.1671	$103.17	$103.15	$103.20
Purchase #4	$205.80	10.588%	$227.5901	$227.59	$227.60	$227.60
Purchase #5	$92.34	13.111%	$104.4467	$104.45	$104.45	$104.40
Purchase #6	$171.71	7.809%	$185.1188	$185.12	$185.10	$185.10
Purchase #7	$155.66	7.582%	$167.4621	$167.46	$167.45	$167.50
7 purchase totals =	$965.63		$1,048.2287	$1,048.23	$1,048.20	$1,048.20