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	$92.62	5.833%	$98.0225	$98.02	$98.00	$98.00
Purchase #2	$234.82	3.527%	$243.1021	$243.10	$243.10	$243.10
Purchase #3	$36.78	7.271%	$39.4543	$39.45	$39.45	$39.50
Purchase #4	$100.56	5.287%	$105.8766	$105.88	$105.90	$105.90
Purchase #5	$90.44	7.416%	$97.147	$97.15	$97.15	$97.10
Purchase #6	$204.40	5.817%	$216.2899	$216.29	$216.30	$216.30
Purchase #7	$242.62	6.799%	$259.1157	$259.12	$259.10	$259.10
7 purchase totals =	$1,002.24		$1,059.0081	$1,059.01	$1,059.00	$1,059.00