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	$199.32	4.316%	$207.9227	$207.92	$207.90	$207.90
Purchase #2	$90.30	11.213%	$100.4253	$100.43	$100.45	$100.40
Purchase #3	$20.50	6.614%	$21.8559	$21.86	$21.85	$21.90
Purchase #4	$174.36	12.439%	$196.0486	$196.05	$196.05	$196.00
Purchase #5	$152.40	11.498%	$169.923	$169.92	$169.90	$169.90
Purchase #6	$113.85	4.455%	$118.922	$118.92	$118.90	$118.90
Purchase #7	$175.73	9.823%	$192.992	$192.99	$193.00	$193.00
7 purchase totals =	$926.46		$1,008.0895	$1,008.09	$1,008.05	$1,008.00