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	$199.47	8.227%	$215.8804	$215.88	$215.90	$215.90
Purchase #2	$60.38	6.761%	$64.4623	$64.46	$64.45	$64.50
Purchase #3	$26.53	10.271%	$29.2549	$29.25	$29.25	$29.30
Purchase #4	$49.97	10.498%	$55.2159	$55.22	$55.20	$55.20
Purchase #5	$48.94	9.559%	$53.6182	$53.62	$53.60	$53.60
Purchase #6	$61.59	5.794%	$65.1585	$65.16	$65.15	$65.20
Purchase #7	$178.95	7.234%	$191.8952	$191.90	$191.90	$191.90
7 purchase totals =	$625.83		$675.4854	$675.49	$675.45	$675.60