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	$142.42	5.804%	$150.6861	$150.69	$150.70	$150.70
Purchase #2	$184.40	8.779%	$200.5885	$200.59	$200.60	$200.60
Purchase #3	$33.38	9.869%	$36.6743	$36.67	$36.65	$36.70
Purchase #4	$79.58	3.820%	$82.62	$82.62	$82.60	$82.60
Purchase #5	$247.47	10.321%	$273.0114	$273.01	$273.00	$273.00
Purchase #6	$149.85	7.261%	$160.7306	$160.73	$160.75	$160.70
Purchase #7	$99.45	3.841%	$103.2699	$103.27	$103.25	$103.30
7 purchase totals =	$936.55		$1,007.5808	$1,007.58	$1,007.55	$1,007.60