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	$67.76	6.275%	$72.0119	$72.01	$72.00	$72.00
Purchase #2	$111.74	10.283%	$123.2302	$123.23	$123.25	$123.20
Purchase #3	$250.82	9.423%	$274.4548	$274.45	$274.45	$274.50
Purchase #4	$64.92	12.119%	$72.7877	$72.79	$72.80	$72.80
Purchase #5	$161.59	10.270%	$178.1853	$178.19	$178.20	$178.20
Purchase #6	$236.40	10.805%	$261.943	$261.94	$261.95	$261.90
Purchase #7	$83.27	7.379%	$89.4145	$89.41	$89.40	$89.40
7 purchase totals =	$976.50		$1,072.0274	$1,072.02	$1,072.05	$1,072.00