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	$118.29	12.691%	$133.3022	$133.30	$133.30	$133.30
Purchase #2	$19.37	7.256%	$20.7755	$20.78	$20.80	$20.80
Purchase #3	$161.58	10.463%	$178.4861	$178.49	$178.50	$178.50
Purchase #4	$110.33	11.528%	$123.0488	$123.05	$123.05	$123.00
Purchase #5	$89.36	6.701%	$95.348	$95.35	$95.35	$95.30
Purchase #6	$245.83	5.551%	$259.476	$259.48	$259.50	$259.50
Purchase #7	$242.81	13.128%	$274.6861	$274.69	$274.70	$274.70
7 purchase totals =	$987.57		$1,085.1227	$1,085.14	$1,085.20	$1,085.10