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	$67.80	8.563%	$73.6057	$73.61	$73.60	$73.60
Purchase #2	$111.27	8.364%	$120.5766	$120.58	$120.60	$120.60
Purchase #3	$89.98	7.618%	$96.8347	$96.83	$96.85	$96.80
Purchase #4	$192.52	13.530%	$218.568	$218.57	$218.55	$218.60
Purchase #5	$50.62	5.225%	$53.2649	$53.26	$53.25	$53.30
Purchase #6	$111.59	12.826%	$125.9025	$125.90	$125.90	$125.90
Purchase #7	$223.56	4.334%	$233.2491	$233.25	$233.25	$233.20
7 purchase totals =	$847.34		$922.0015	$922.00	$922.00	$922.00