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	$64.42	9.375%	$70.4594	$70.46	$70.45	$70.50
Purchase #2	$229.27	11.351%	$255.2944	$255.29	$255.30	$255.30
Purchase #3	$61.51	5.334%	$64.7909	$64.79	$64.80	$64.80
Purchase #4	$158.42	6.209%	$168.2563	$168.26	$168.25	$168.30
Purchase #5	$211.30	5.772%	$223.4962	$223.50	$223.50	$223.50
Purchase #6	$163.76	10.650%	$181.2004	$181.20	$181.20	$181.20
Purchase #7	$41.81	9.410%	$45.7443	$45.74	$45.75	$45.70
7 purchase totals =	$930.49		$1,009.2419	$1,009.24	$1,009.25	$1,009.30