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	$202.91	5.263%	$213.5892	$213.59	$213.60	$213.60
Purchase #2	$176.67	3.439%	$182.7457	$182.75	$182.75	$182.70
Purchase #3	$148.37	11.421%	$165.3153	$165.32	$165.30	$165.30
Purchase #4	$29.27	10.115%	$32.2307	$32.23	$32.25	$32.20
Purchase #5	$193.83	11.579%	$216.2736	$216.27	$216.25	$216.30
Purchase #6	$160.78	7.502%	$172.8417	$172.84	$172.85	$172.80
Purchase #7	$89.78	6.215%	$95.3598	$95.36	$95.35	$95.40
7 purchase totals =	$1,001.61		$1,078.3560	$1,078.36	$1,078.35	$1,078.30