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	$68.46	7.134%	$73.3439	$73.34	$73.35	$73.30
Purchase #2	$104.66	7.752%	$112.7732	$112.77	$112.75	$112.80
Purchase #3	$66.46	4.245%	$69.2812	$69.28	$69.30	$69.30
Purchase #4	$77.40	8.367%	$83.8761	$83.88	$83.90	$83.90
Purchase #5	$79.62	12.322%	$89.4308	$89.43	$89.45	$89.40
Purchase #6	$70.51	11.162%	$78.3803	$78.38	$78.40	$78.40
Purchase #7	$248.32	7.665%	$267.3537	$267.35	$267.35	$267.40
7 purchase totals =	$715.43		$774.4392	$774.43	$774.50	$774.50