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	$148.51	9.417%	$162.4952	$162.50	$162.50	$162.50
Purchase #2	$32.55	9.120%	$35.5186	$35.52	$35.50	$35.50
Purchase #3	$100.57	9.686%	$110.3112	$110.31	$110.30	$110.30
Purchase #4	$240.35	6.232%	$255.3286	$255.33	$255.35	$255.30
Purchase #5	$137.63	10.744%	$152.417	$152.42	$152.40	$152.40
Purchase #6	$33.90	6.313%	$36.0401	$36.04	$36.05	$36.00
Purchase #7	$204.40	10.550%	$225.9642	$225.96	$225.95	$226.00
7 purchase totals =	$897.91		$978.0749	$978.08	$978.05	$978.00