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	$44.46	4.205%	$46.3295	$46.33	$46.35	$46.30
Purchase #2	$28.45	13.397%	$32.2614	$32.26	$32.25	$32.30
Purchase #3	$142.28	13.744%	$161.835	$161.84	$161.85	$161.80
Purchase #4	$33.69	12.428%	$37.877	$37.88	$37.90	$37.90
Purchase #5	$56.75	10.815%	$62.8875	$62.89	$62.90	$62.90
Purchase #6	$20.96	10.436%	$23.1474	$23.15	$23.15	$23.10
Purchase #7	$215.31	6.176%	$228.6075	$228.61	$228.60	$228.60
7 purchase totals =	$541.90		$592.9453	$592.96	$593.00	$592.90