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	$214.69	8.692%	$233.3509	$233.35	$233.35	$233.40
Purchase #2	$105.56	5.459%	$111.3225	$111.32	$111.30	$111.30
Purchase #3	$139.56	3.700%	$144.7237	$144.72	$144.70	$144.70
Purchase #4	$202.97	4.200%	$211.4947	$211.49	$211.50	$211.50
Purchase #5	$104.40	4.866%	$109.4801	$109.48	$109.50	$109.50
Purchase #6	$92.82	9.348%	$101.4968	$101.50	$101.50	$101.50
Purchase #7	$129.48	9.537%	$141.8285	$141.83	$141.85	$141.80
7 purchase totals =	$989.48		$1,053.6972	$1,053.69	$1,053.70	$1,053.70