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	$51.26	7.731%	$55.2229	$55.22	$55.20	$55.20
Purchase #2	$172.27	10.350%	$190.0999	$190.10	$190.10	$190.10
Purchase #3	$96.83	13.407%	$109.812	$109.81	$109.80	$109.80
Purchase #4	$51.68	9.846%	$56.7684	$56.77	$56.75	$56.80
Purchase #5	$69.59	3.256%	$71.8559	$71.86	$71.85	$71.90
Purchase #6	$102.56	13.449%	$116.3533	$116.35	$116.35	$116.40
Purchase #7	$73.51	5.376%	$77.4619	$77.46	$77.45	$77.50
7 purchase totals =	$617.70		$677.5743	$677.57	$677.50	$677.70