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	$105.83	6.603%	$112.818	$112.82	$112.80	$112.80
Purchase #2	$61.49	4.514%	$64.2657	$64.27	$64.25	$64.30
Purchase #3	$182.72	8.492%	$198.2366	$198.24	$198.25	$198.20
Purchase #4	$127.50	3.439%	$131.8847	$131.88	$131.90	$131.90
Purchase #5	$80.67	13.236%	$91.3475	$91.35	$91.35	$91.30
Purchase #6	$78.31	3.466%	$81.0242	$81.02	$81.00	$81.00
Purchase #7	$227.30	13.114%	$257.1081	$257.11	$257.10	$257.10
7 purchase totals =	$863.82		$936.6848	$936.69	$936.65	$936.60