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	$93.44	6.204%	$99.237	$99.24	$99.25	$99.20
Purchase #2	$97.75	11.520%	$109.0108	$109.01	$109.00	$109.00
Purchase #3	$101.98	9.455%	$111.6222	$111.62	$111.60	$111.60
Purchase #4	$110.59	11.611%	$123.4306	$123.43	$123.45	$123.40
Purchase #5	$188.48	12.212%	$211.4972	$211.50	$211.50	$211.50
Purchase #6	$133.65	12.163%	$149.9058	$149.91	$149.90	$149.90
Purchase #7	$227.26	12.320%	$255.2584	$255.26	$255.25	$255.30
7 purchase totals =	$953.15		$1,059.9620	$1,059.97	$1,059.95	$1,059.90