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	$197.96	13.298%	$224.2847	$224.28	$224.30	$224.30
Purchase #2	$81.46	11.284%	$90.6519	$90.65	$90.65	$90.70
Purchase #3	$165.51	3.610%	$171.4849	$171.48	$171.50	$171.50
Purchase #4	$7.54	9.518%	$8.2577	$8.26	$8.25	$8.30
Purchase #5	$186.59	13.308%	$211.4214	$211.42	$211.40	$211.40
Purchase #6	$47.84	3.388%	$49.4608	$49.46	$49.45	$49.50
Purchase #7	$137.50	10.717%	$152.2359	$152.24	$152.25	$152.20
7 purchase totals =	$824.40		$907.7973	$907.79	$907.80	$907.90