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	$90.96	4.132%	$94.7185	$94.72	$94.70	$94.70
Purchase #2	$39.38	5.692%	$41.6215	$41.62	$41.60	$41.60
Purchase #3	$90.92	6.188%	$96.5461	$96.55	$96.55	$96.50
Purchase #4	$216.73	12.759%	$244.3826	$244.38	$244.40	$244.40
Purchase #5	$38.85	4.384%	$40.5532	$40.55	$40.55	$40.60
Purchase #6	$228.98	13.250%	$259.3199	$259.32	$259.30	$259.30
Purchase #7	$180.63	6.495%	$192.3619	$192.36	$192.35	$192.40
7 purchase totals =	$886.45		$969.5037	$969.50	$969.45	$969.50