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	$134.77	13.755%	$153.3076	$153.31	$153.30	$153.30
Purchase #2	$56.63	10.752%	$62.7189	$62.72	$62.70	$62.70
Purchase #3	$184.41	11.342%	$205.3258	$205.33	$205.35	$205.30
Purchase #4	$204.59	10.748%	$226.5793	$226.58	$226.60	$226.60
Purchase #5	$192.87	11.780%	$215.5901	$215.59	$215.60	$215.60
Purchase #6	$88.43	7.713%	$95.2506	$95.25	$95.25	$95.30
Purchase #7	$53.48	4.348%	$55.8053	$55.81	$55.80	$55.80
7 purchase totals =	$915.18		$1,014.5776	$1,014.59	$1,014.60	$1,014.60