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	$47.60	3.773%	$49.3959	$49.40	$49.40	$49.40
Purchase #2	$136.73	13.822%	$155.6288	$155.63	$155.65	$155.60
Purchase #3	$190.99	11.289%	$212.5509	$212.55	$212.55	$212.60
Purchase #4	$153.98	8.853%	$167.6118	$167.61	$167.60	$167.60
Purchase #5	$83.66	6.799%	$89.348	$89.35	$89.35	$89.30
Purchase #6	$143.30	11.656%	$160.003	$160.00	$160.00	$160.00
Purchase #7	$54.74	9.249%	$59.8029	$59.80	$59.80	$59.80
7 purchase totals =	$811.00		$894.3413	$894.34	$894.35	$894.30