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	$243.76	12.718%	$274.7614	$274.76	$274.75	$274.80
Purchase #2	$118.45	11.305%	$131.8408	$131.84	$131.85	$131.80
Purchase #3	$86.57	6.498%	$92.1953	$92.20	$92.20	$92.20
Purchase #4	$56.52	5.138%	$59.424	$59.42	$59.40	$59.40
Purchase #5	$18.33	6.797%	$19.5759	$19.58	$19.60	$19.60
Purchase #6	$126.85	13.305%	$143.7274	$143.73	$143.75	$143.70
Purchase #7	$221.77	9.582%	$243.02	$243.02	$243.00	$243.00
7 purchase totals =	$872.25		$964.5448	$964.55	$964.55	$964.50