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	$103.85	10.310%	$114.5569	$114.56	$114.55	$114.60
Purchase #2	$176.95	4.715%	$185.2932	$185.29	$185.30	$185.30
Purchase #3	$100.86	10.252%	$111.2002	$111.20	$111.20	$111.20
Purchase #4	$81.76	5.731%	$86.4457	$86.45	$86.45	$86.40
Purchase #5	$200.30	7.565%	$215.4527	$215.45	$215.45	$215.50
Purchase #6	$128.87	10.335%	$142.1887	$142.19	$142.20	$142.20
Purchase #7	$186.96	6.491%	$199.0956	$199.10	$199.10	$199.10
7 purchase totals =	$979.55		$1,054.2330	$1,054.24	$1,054.25	$1,054.30