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	$223.80	7.481%	$240.5425	$240.54	$240.55	$240.50
Purchase #2	$112.67	11.794%	$125.9583	$125.96	$125.95	$126.00
Purchase #3	$59.76	6.700%	$63.7639	$63.76	$63.75	$63.80
Purchase #4	$27.78	9.396%	$30.3902	$30.39	$30.40	$30.40
Purchase #5	$114.52	7.587%	$123.2086	$123.21	$123.20	$123.20
Purchase #6	$172.73	4.161%	$179.9173	$179.92	$179.90	$179.90
Purchase #7	$96.25	9.677%	$105.5641	$105.56	$105.55	$105.60
7 purchase totals =	$807.51		$869.3449	$869.34	$869.30	$869.40