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	$177.44	4.704%	$185.7868	$185.79	$185.80	$185.80
Purchase #2	$150.83	9.841%	$165.6732	$165.67	$165.65	$165.70
Purchase #3	$51.66	7.744%	$55.6606	$55.66	$55.65	$55.70
Purchase #4	$36.33	8.630%	$39.4653	$39.47	$39.45	$39.50
Purchase #5	$67.37	6.811%	$71.9586	$71.96	$71.95	$72.00
Purchase #6	$28.68	12.671%	$32.314	$32.31	$32.30	$32.30
Purchase #7	$144.32	6.632%	$153.8913	$153.89	$153.90	$153.90
7 purchase totals =	$656.63		$704.7498	$704.75	$704.70	$704.90