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	$152.69	12.693%	$172.0709	$172.07	$172.05	$172.10
Purchase #2	$223.59	9.670%	$245.2112	$245.21	$245.20	$245.20
Purchase #3	$59.89	13.399%	$67.9147	$67.91	$67.90	$67.90
Purchase #4	$84.74	9.217%	$92.5505	$92.55	$92.55	$92.60
Purchase #5	$49.37	8.237%	$53.4366	$53.44	$53.45	$53.40
Purchase #6	$211.79	3.636%	$219.4907	$219.49	$219.50	$219.50
Purchase #7	$170.31	6.759%	$181.8213	$181.82	$181.80	$181.80
7 purchase totals =	$952.38		$1,032.4959	$1,032.49	$1,032.45	$1,032.50