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	$248.29	5.345%	$261.5611	$261.56	$261.55	$261.60
Purchase #2	$185.75	6.727%	$198.2454	$198.25	$198.25	$198.20
Purchase #3	$29.31	10.148%	$32.2844	$32.28	$32.30	$32.30
Purchase #4	$123.50	6.289%	$131.2669	$131.27	$131.25	$131.30
Purchase #5	$116.94	9.532%	$128.0867	$128.09	$128.10	$128.10
Purchase #6	$79.53	3.486%	$82.3024	$82.30	$82.30	$82.30
Purchase #7	$70.30	3.383%	$72.6782	$72.68	$72.70	$72.70
7 purchase totals =	$853.62		$906.4251	$906.43	$906.45	$906.50