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	$47.37	3.209%	$48.8901	$48.89	$48.90	$48.90
Purchase #2	$25.69	9.335%	$28.0882	$28.09	$28.10	$28.10
Purchase #3	$5.73	5.549%	$6.048	$6.05	$6.05	$6.00
Purchase #4	$59.98	9.333%	$65.5779	$65.58	$65.60	$65.60
Purchase #5	$65.61	10.557%	$72.5364	$72.54	$72.55	$72.50
Purchase #6	$105.73	4.599%	$110.5925	$110.59	$110.60	$110.60
Purchase #7	$30.57	11.408%	$34.0574	$34.06	$34.05	$34.10
7 purchase totals =	$340.68		$365.7905	$365.80	$365.85	$365.80