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	$242.56	7.506%	$260.7666	$260.77	$260.75	$260.80
Purchase #2	$68.72	8.607%	$74.6347	$74.63	$74.65	$74.60
Purchase #3	$83.66	7.663%	$90.0709	$90.07	$90.05	$90.10
Purchase #4	$221.57	3.321%	$228.9283	$228.93	$228.95	$228.90
Purchase #5	$153.31	6.159%	$162.7524	$162.75	$162.75	$162.80
Purchase #6	$165.51	3.606%	$171.4783	$171.48	$171.50	$171.50
Purchase #7	$87.51	11.434%	$97.5159	$97.52	$97.50	$97.50
7 purchase totals =	$1,022.84		$1,086.1471	$1,086.15	$1,086.15	$1,086.20