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	$85.33	6.552%	$90.9208	$90.92	$90.90	$90.90
Purchase #2	$48.59	4.741%	$50.8937	$50.89	$50.90	$50.90
Purchase #3	$134.99	13.573%	$153.3122	$153.31	$153.30	$153.30
Purchase #4	$169.65	9.586%	$185.9126	$185.91	$185.90	$185.90
Purchase #5	$185.57	9.363%	$202.9449	$202.94	$202.95	$202.90
Purchase #6	$160.28	11.839%	$179.2555	$179.26	$179.25	$179.30
Purchase #7	$86.43	11.364%	$96.2519	$96.25	$96.25	$96.30
7 purchase totals =	$870.84		$959.4916	$959.48	$959.45	$959.50