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	$75.55	9.752%	$82.9176	$82.92	$82.90	$82.90
Purchase #2	$98.41	11.570%	$109.796	$109.80	$109.80	$109.80
Purchase #3	$58.51	7.668%	$62.9965	$63.00	$63.00	$63.00
Purchase #4	$64.71	10.589%	$71.5621	$71.56	$71.55	$71.60
Purchase #5	$69.80	3.481%	$72.2297	$72.23	$72.25	$72.20
Purchase #6	$197.95	13.126%	$223.9329	$223.93	$223.95	$223.90
Purchase #7	$95.99	4.229%	$100.0494	$100.05	$100.05	$100.00
7 purchase totals =	$660.92		$723.4842	$723.49	$723.50	$723.40