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	$109.88	3.594%	$113.8291	$113.83	$113.85	$113.80
Purchase #2	$169.32	9.633%	$185.6306	$185.63	$185.65	$185.60
Purchase #3	$89.65	5.735%	$94.7914	$94.79	$94.80	$94.80
Purchase #4	$154.60	6.442%	$164.5593	$164.56	$164.55	$164.60
Purchase #5	$94.45	13.265%	$106.9788	$106.98	$107.00	$107.00
Purchase #6	$217.29	8.376%	$235.4902	$235.49	$235.50	$235.50
Purchase #7	$115.81	13.224%	$131.1247	$131.12	$131.10	$131.10
7 purchase totals =	$951.00		$1,032.4041	$1,032.40	$1,032.45	$1,032.40