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	$160.55	7.228%	$172.1546	$172.15	$172.15	$172.20
Purchase #2	$156.46	11.244%	$174.0524	$174.05	$174.05	$174.10
Purchase #3	$150.78	13.117%	$170.5578	$170.56	$170.55	$170.60
Purchase #4	$250.77	9.715%	$275.1323	$275.13	$275.15	$275.10
Purchase #5	$220.82	9.424%	$241.6301	$241.63	$241.65	$241.60
Purchase #6	$27.69	4.670%	$28.9831	$28.98	$29.00	$29.00
Purchase #7	$111.57	6.112%	$118.3892	$118.39	$118.40	$118.40
7 purchase totals =	$1,078.64		$1,180.8995	$1,180.89	$1,180.95	$1,181.00