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	$118.50	4.225%	$123.5066	$123.51	$123.50	$123.50
Purchase #2	$216.30	3.109%	$223.0248	$223.02	$223.00	$223.00
Purchase #3	$89.88	12.645%	$101.2453	$101.25	$101.25	$101.20
Purchase #4	$176.66	13.575%	$200.6416	$200.64	$200.65	$200.60
Purchase #5	$159.83	13.612%	$181.5861	$181.59	$181.60	$181.60
Purchase #6	$132.51	11.530%	$147.7884	$147.79	$147.80	$147.80
Purchase #7	$27.67	9.779%	$30.3758	$30.38	$30.40	$30.40
7 purchase totals =	$921.35		$1,008.1686	$1,008.18	$1,008.20	$1,008.10