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	$85.33	10.460%	$94.2555	$94.26	$94.25	$94.30
Purchase #2	$57.50	8.711%	$62.5088	$62.51	$62.50	$62.50
Purchase #3	$250.57	6.396%	$266.5965	$266.60	$266.60	$266.60
Purchase #4	$14.78	7.599%	$15.9031	$15.90	$15.90	$15.90
Purchase #5	$51.91	12.376%	$58.3344	$58.33	$58.35	$58.30
Purchase #6	$228.76	6.172%	$242.8791	$242.88	$242.90	$242.90
Purchase #7	$39.37	7.289%	$42.2397	$42.24	$42.25	$42.20
7 purchase totals =	$728.22		$782.7171	$782.72	$782.75	$782.70