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	$220.34	4.524%	$230.3082	$230.31	$230.30	$230.30
Purchase #2	$187.56	6.797%	$200.3085	$200.31	$200.30	$200.30
Purchase #3	$65.74	13.198%	$74.4164	$74.42	$74.40	$74.40
Purchase #4	$178.87	8.797%	$194.6052	$194.61	$194.60	$194.60
Purchase #5	$57.74	13.569%	$65.5747	$65.57	$65.55	$65.60
Purchase #6	$81.25	10.515%	$89.7934	$89.79	$89.80	$89.80
Purchase #7	$74.98	3.367%	$77.5046	$77.50	$77.50	$77.50
7 purchase totals =	$866.48		$932.5110	$932.51	$932.45	$932.50