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	$126.87	13.747%	$144.3108	$144.31	$144.30	$144.30
Purchase #2	$47.77	12.199%	$53.5975	$53.60	$53.60	$53.60
Purchase #3	$225.60	8.838%	$245.5385	$245.54	$245.55	$245.50
Purchase #4	$233.59	12.119%	$261.8988	$261.90	$261.90	$261.90
Purchase #5	$61.30	10.249%	$67.5826	$67.58	$67.60	$67.60
Purchase #6	$51.91	10.404%	$57.3107	$57.31	$57.30	$57.30
Purchase #7	$229.32	3.698%	$237.8003	$237.80	$237.80	$237.80
7 purchase totals =	$976.36		$1,068.0392	$1,068.04	$1,068.05	$1,068.00