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	$109.60	5.818%	$115.9765	$115.98	$116.00	$116.00
Purchase #2	$37.27	13.701%	$42.3764	$42.38	$42.40	$42.40
Purchase #3	$198.79	12.613%	$223.8634	$223.86	$223.85	$223.90
Purchase #4	$205.98	5.742%	$217.8074	$217.81	$217.80	$217.80
Purchase #5	$214.78	4.388%	$224.2045	$224.20	$224.20	$224.20
Purchase #6	$218.95	3.170%	$225.8907	$225.89	$225.90	$225.90
Purchase #7	$33.33	13.288%	$37.7589	$37.76	$37.75	$37.80
7 purchase totals =	$1,018.70		$1,087.8778	$1,087.88	$1,087.90	$1,088.00