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	$153.80	10.106%	$169.343	$169.34	$169.35	$169.30
Purchase #2	$45.56	7.390%	$48.9269	$48.93	$48.95	$48.90
Purchase #3	$86.71	13.397%	$98.3265	$98.33	$98.35	$98.30
Purchase #4	$236.42	4.664%	$247.4466	$247.45	$247.45	$247.40
Purchase #5	$79.89	3.768%	$82.9003	$82.90	$82.90	$82.90
Purchase #6	$248.44	4.383%	$259.3291	$259.33	$259.35	$259.30
Purchase #7	$40.60	3.182%	$41.8919	$41.89	$41.90	$41.90
7 purchase totals =	$891.42		$948.1643	$948.17	$948.25	$948.00