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	$86.74	6.198%	$92.1161	$92.12	$92.10	$92.10
Purchase #2	$12.48	6.151%	$13.2476	$13.25	$13.25	$13.20
Purchase #3	$91.89	6.653%	$98.0034	$98.00	$98.00	$98.00
Purchase #4	$195.45	12.603%	$220.0826	$220.08	$220.10	$220.10
Purchase #5	$124.49	5.339%	$131.1365	$131.14	$131.15	$131.10
Purchase #6	$65.64	8.660%	$71.3244	$71.32	$71.30	$71.30
Purchase #7	$105.56	5.584%	$111.4545	$111.45	$111.45	$111.50
7 purchase totals =	$682.25		$737.3651	$737.36	$737.35	$737.30