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	$120.74	5.818%	$127.7647	$127.76	$127.75	$127.80
Purchase #2	$42.38	12.472%	$47.6656	$47.67	$47.65	$47.70
Purchase #3	$62.50	9.793%	$68.6206	$68.62	$68.60	$68.60
Purchase #4	$16.89	9.712%	$18.5304	$18.53	$18.55	$18.50
Purchase #5	$137.95	9.328%	$150.818	$150.82	$150.80	$150.80
Purchase #6	$212.85	11.774%	$237.911	$237.91	$237.90	$237.90
Purchase #7	$147.72	5.378%	$155.6644	$155.66	$155.65	$155.70
7 purchase totals =	$741.03		$806.9747	$806.97	$806.90	$807.00