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	$209.98	5.289%	$221.0858	$221.09	$221.10	$221.10
Purchase #2	$236.75	3.693%	$245.4932	$245.49	$245.50	$245.50
Purchase #3	$222.82	8.525%	$241.8154	$241.82	$241.80	$241.80
Purchase #4	$89.81	10.870%	$99.5723	$99.57	$99.55	$99.60
Purchase #5	$86.69	8.273%	$93.8619	$93.86	$93.85	$93.90
Purchase #6	$89.33	12.279%	$100.2988	$100.30	$100.30	$100.30
Purchase #7	$12.99	8.126%	$14.0456	$14.05	$14.05	$14.00
7 purchase totals =	$948.37		$1,016.1730	$1,016.18	$1,016.15	$1,016.20