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	$216.94	8.746%	$235.9136	$235.91	$235.90	$235.90
Purchase #2	$56.38	8.294%	$61.0562	$61.06	$61.05	$61.10
Purchase #3	$203.59	4.844%	$213.4519	$213.45	$213.45	$213.50
Purchase #4	$159.39	3.860%	$165.5425	$165.54	$165.55	$165.50
Purchase #5	$104.88	6.748%	$111.9573	$111.96	$111.95	$112.00
Purchase #6	$241.61	8.221%	$261.4728	$261.47	$261.45	$261.50
Purchase #7	$21.75	3.367%	$22.4823	$22.48	$22.50	$22.50
7 purchase totals =	$1,004.54		$1,071.8766	$1,071.87	$1,071.85	$1,072.00