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	$33.38	10.206%	$36.7868	$36.79	$36.80	$36.80
Purchase #2	$226.64	11.590%	$252.9076	$252.91	$252.90	$252.90
Purchase #3	$235.89	12.400%	$265.1404	$265.14	$265.15	$265.10
Purchase #4	$179.88	11.487%	$200.5428	$200.54	$200.55	$200.50
Purchase #5	$187.95	5.607%	$198.4884	$198.49	$198.50	$198.50
Purchase #6	$97.32	7.870%	$104.9791	$104.98	$105.00	$105.00
Purchase #7	$147.85	13.855%	$168.3346	$168.33	$168.35	$168.30
7 purchase totals =	$1,108.91		$1,227.1797	$1,227.18	$1,227.25	$1,227.10