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	$82.41	5.617%	$87.039	$87.04	$87.05	$87.00
Purchase #2	$191.57	4.572%	$200.3286	$200.33	$200.35	$200.30
Purchase #3	$210.40	6.281%	$223.6152	$223.62	$223.60	$223.60
Purchase #4	$74.37	10.469%	$82.1558	$82.16	$82.15	$82.20
Purchase #5	$86.45	8.674%	$93.9487	$93.95	$93.95	$93.90
Purchase #6	$120.72	9.582%	$132.2874	$132.29	$132.30	$132.30
Purchase #7	$198.41	12.567%	$223.3442	$223.34	$223.35	$223.30
7 purchase totals =	$964.33		$1,042.7189	$1,042.73	$1,042.75	$1,042.60