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	$85.42	11.108%	$94.9085	$94.91	$94.90	$94.90
Purchase #2	$20.91	4.351%	$21.8198	$21.82	$21.80	$21.80
Purchase #3	$97.51	12.601%	$109.7972	$109.80	$109.80	$109.80
Purchase #4	$88.89	11.395%	$99.019	$99.02	$99.00	$99.00
Purchase #5	$184.43	12.158%	$206.853	$206.85	$206.85	$206.90
Purchase #6	$229.88	4.287%	$239.735	$239.74	$239.75	$239.70
Purchase #7	$243.31	7.398%	$261.3101	$261.31	$261.30	$261.30
7 purchase totals =	$950.35		$1,033.4426	$1,033.45	$1,033.40	$1,033.40