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	$232.59	5.158%	$244.587	$244.59	$244.60	$244.60
Purchase #2	$194.68	12.603%	$219.2155	$219.22	$219.20	$219.20
Purchase #3	$205.27	11.211%	$228.2828	$228.28	$228.30	$228.30
Purchase #4	$51.59	11.169%	$57.3521	$57.35	$57.35	$57.40
Purchase #5	$223.93	4.293%	$233.5433	$233.54	$233.55	$233.50
Purchase #6	$98.48	6.549%	$104.9295	$104.93	$104.95	$104.90
Purchase #7	$81.40	5.601%	$85.9592	$85.96	$85.95	$86.00
7 purchase totals =	$1,087.94		$1,173.8694	$1,173.87	$1,173.90	$1,173.90