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	$156.70	9.817%	$172.0832	$172.08	$172.10	$172.10
Purchase #2	$143.57	6.559%	$152.9868	$152.99	$153.00	$153.00
Purchase #3	$40.59	8.146%	$43.8965	$43.90	$43.90	$43.90
Purchase #4	$195.61	8.312%	$211.8691	$211.87	$211.85	$211.90
Purchase #5	$149.32	3.699%	$154.8433	$154.84	$154.85	$154.80
Purchase #6	$215.26	10.714%	$238.323	$238.32	$238.30	$238.30
Purchase #7	$99.48	10.289%	$109.7155	$109.72	$109.70	$109.70
7 purchase totals =	$1,000.53		$1,083.7174	$1,083.72	$1,083.70	$1,083.70