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	$236.50	8.441%	$256.463	$256.46	$256.45	$256.50
Purchase #2	$216.34	3.476%	$223.86	$223.86	$223.85	$223.90
Purchase #3	$231.78	13.821%	$263.8143	$263.81	$263.80	$263.80
Purchase #4	$116.55	9.678%	$127.8297	$127.83	$127.85	$127.80
Purchase #5	$6.45	10.552%	$7.1306	$7.13	$7.15	$7.10
Purchase #6	$188.42	8.868%	$205.1291	$205.13	$205.15	$205.10
Purchase #7	$65.94	3.336%	$68.1398	$68.14	$68.15	$68.10
7 purchase totals =	$1,061.98		$1,152.3665	$1,152.36	$1,152.40	$1,152.30