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	$189.35	11.660%	$211.4282	$211.43	$211.45	$211.40
Purchase #2	$82.82	12.478%	$93.1543	$93.15	$93.15	$93.20
Purchase #3	$51.50	5.753%	$54.4628	$54.46	$54.45	$54.50
Purchase #4	$126.80	10.362%	$139.939	$139.94	$139.95	$139.90
Purchase #5	$161.38	4.276%	$168.2806	$168.28	$168.30	$168.30
Purchase #6	$220.81	10.527%	$244.0547	$244.05	$244.05	$244.10
Purchase #7	$88.59	8.473%	$96.0962	$96.10	$96.10	$96.10
7 purchase totals =	$921.25		$1,007.4158	$1,007.41	$1,007.45	$1,007.50