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	$74.89	10.258%	$82.5722	$82.57	$82.55	$82.60
Purchase #2	$81.76	11.638%	$91.2752	$91.28	$91.30	$91.30
Purchase #3	$51.57	11.616%	$57.5604	$57.56	$57.55	$57.60
Purchase #4	$86.40	10.499%	$95.4711	$95.47	$95.45	$95.50
Purchase #5	$94.94	13.570%	$107.8234	$107.82	$107.80	$107.80
Purchase #6	$26.71	6.612%	$28.4761	$28.48	$28.50	$28.50
Purchase #7	$142.83	5.649%	$150.8985	$150.90	$150.90	$150.90
7 purchase totals =	$559.10		$614.0769	$614.08	$614.05	$614.20