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	$67.37	3.237%	$69.5508	$69.55	$69.55	$69.60
Purchase #2	$35.27	5.707%	$37.2829	$37.28	$37.30	$37.30
Purchase #3	$158.63	11.281%	$176.5251	$176.53	$176.55	$176.50
Purchase #4	$154.77	9.278%	$169.1296	$169.13	$169.15	$169.10
Purchase #5	$209.92	12.183%	$235.4946	$235.49	$235.50	$235.50
Purchase #6	$144.26	12.671%	$162.5392	$162.54	$162.55	$162.50
Purchase #7	$18.39	10.488%	$20.3187	$20.32	$20.30	$20.30
7 purchase totals =	$788.61		$870.8409	$870.84	$870.90	$870.80