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	$238.41	11.473%	$265.7628	$265.76	$265.75	$265.80
Purchase #2	$109.45	12.425%	$123.0492	$123.05	$123.05	$123.00
Purchase #3	$152.94	4.701%	$160.1297	$160.13	$160.15	$160.10
Purchase #4	$38.60	10.487%	$42.648	$42.65	$42.65	$42.60
Purchase #5	$162.53	8.416%	$176.2085	$176.21	$176.20	$176.20
Purchase #6	$162.38	12.415%	$182.5395	$182.54	$182.55	$182.50
Purchase #7	$114.26	13.802%	$130.0302	$130.03	$130.05	$130.00
7 purchase totals =	$978.57		$1,080.3679	$1,080.37	$1,080.40	$1,080.20