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	$66.71	13.687%	$75.8406	$75.84	$75.85	$75.80
Purchase #2	$205.86	7.511%	$221.3221	$221.32	$221.30	$221.30
Purchase #3	$178.36	10.278%	$196.6918	$196.69	$196.70	$196.70
Purchase #4	$214.68	13.320%	$243.2754	$243.28	$243.30	$243.30
Purchase #5	$90.27	10.858%	$100.0715	$100.07	$100.05	$100.10
Purchase #6	$91.28	3.819%	$94.766	$94.77	$94.75	$94.80
Purchase #7	$218.82	7.785%	$235.8551	$235.86	$235.85	$235.90
7 purchase totals =	$1,065.98		$1,167.8225	$1,167.83	$1,167.80	$1,167.90