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	$142.36	6.716%	$151.9209	$151.92	$151.90	$151.90
Purchase #2	$180.36	10.841%	$199.9128	$199.91	$199.90	$199.90
Purchase #3	$53.77	11.201%	$59.7928	$59.79	$59.80	$59.80
Purchase #4	$7.78	7.844%	$8.3903	$8.39	$8.40	$8.40
Purchase #5	$189.50	9.388%	$207.2903	$207.29	$207.30	$207.30
Purchase #6	$196.93	9.610%	$215.855	$215.86	$215.85	$215.90
Purchase #7	$207.75	4.114%	$216.2968	$216.30	$216.30	$216.30
7 purchase totals =	$978.45		$1,059.4589	$1,059.46	$1,059.45	$1,059.50