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	$91.35	5.702%	$96.5588	$96.56	$96.55	$96.60
Purchase #2	$28.98	10.486%	$32.0188	$32.02	$32.00	$32.00
Purchase #3	$80.82	13.438%	$91.6806	$91.68	$91.70	$91.70
Purchase #4	$92.48	11.509%	$103.1235	$103.12	$103.10	$103.10
Purchase #5	$167.76	13.345%	$190.1476	$190.15	$190.15	$190.10
Purchase #6	$152.58	13.312%	$172.8914	$172.89	$172.90	$172.90
Purchase #7	$233.82	7.836%	$252.1421	$252.14	$252.15	$252.10
7 purchase totals =	$847.79		$938.5628	$938.56	$938.55	$938.50