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	$218.34	11.115%	$242.6085	$242.61	$242.60	$242.60
Purchase #2	$49.52	13.118%	$56.016	$56.02	$56.00	$56.00
Purchase #3	$171.36	10.815%	$189.8926	$189.89	$189.90	$189.90
Purchase #4	$199.61	11.538%	$222.641	$222.64	$222.65	$222.60
Purchase #5	$196.65	7.688%	$211.7685	$211.77	$211.75	$211.80
Purchase #6	$172.58	10.534%	$190.7596	$190.76	$190.75	$190.80
Purchase #7	$86.28	9.205%	$94.2221	$94.22	$94.20	$94.20
7 purchase totals =	$1,094.34		$1,207.9083	$1,207.91	$1,207.85	$1,207.90