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	$116.81	11.487%	$130.228	$130.23	$130.25	$130.20
Purchase #2	$36.82	5.671%	$38.9081	$38.91	$38.90	$38.90
Purchase #3	$144.32	10.214%	$159.0608	$159.06	$159.05	$159.10
Purchase #4	$183.26	9.131%	$199.9935	$199.99	$200.00	$200.00
Purchase #5	$115.86	6.483%	$123.3712	$123.37	$123.35	$123.40
Purchase #6	$230.90	4.529%	$241.3575	$241.36	$241.35	$241.40
Purchase #7	$75.28	13.563%	$85.4902	$85.49	$85.50	$85.50
7 purchase totals =	$903.25		$978.4093	$978.41	$978.40	$978.50