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	$76.78	6.618%	$81.8613	$81.86	$81.85	$81.90
Purchase #2	$123.54	8.130%	$133.5838	$133.58	$133.60	$133.60
Purchase #3	$102.53	3.343%	$105.9576	$105.96	$105.95	$106.00
Purchase #4	$118.31	8.238%	$128.0564	$128.06	$128.05	$128.10
Purchase #5	$210.91	5.621%	$222.7653	$222.77	$222.75	$222.80
Purchase #6	$245.81	11.370%	$273.7586	$273.76	$273.75	$273.80
Purchase #7	$198.50	6.765%	$211.9285	$211.93	$211.95	$211.90
7 purchase totals =	$1,076.38		$1,157.9115	$1,157.92	$1,157.90	$1,158.10