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	$147.92	7.851%	$159.5332	$159.53	$159.55	$159.50
Purchase #2	$83.34	7.252%	$89.3838	$89.38	$89.40	$89.40
Purchase #3	$156.64	4.850%	$164.237	$164.24	$164.25	$164.20
Purchase #4	$94.46	6.499%	$100.599	$100.60	$100.60	$100.60
Purchase #5	$26.47	7.463%	$28.4455	$28.45	$28.45	$28.40
Purchase #6	$247.80	13.610%	$281.5256	$281.53	$281.55	$281.50
Purchase #7	$46.90	5.745%	$49.5944	$49.59	$49.60	$49.60
7 purchase totals =	$803.53		$873.3185	$873.32	$873.40	$873.20