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	$64.98	9.525%	$71.1693	$71.17	$71.15	$71.20
Purchase #2	$16.90	5.815%	$17.8827	$17.88	$17.90	$17.90
Purchase #3	$85.37	4.438%	$89.1587	$89.16	$89.15	$89.20
Purchase #4	$65.67	10.560%	$72.6048	$72.60	$72.60	$72.60
Purchase #5	$16.83	13.550%	$19.1105	$19.11	$19.10	$19.10
Purchase #6	$219.72	8.375%	$238.1216	$238.12	$238.10	$238.10
Purchase #7	$52.59	7.866%	$56.7267	$56.73	$56.75	$56.70
7 purchase totals =	$522.06		$564.7743	$564.77	$564.75	$564.80