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	$164.41	7.279%	$176.3774	$176.38	$176.40	$176.40
Purchase #2	$197.56	9.578%	$216.4823	$216.48	$216.50	$216.50
Purchase #3	$42.58	5.421%	$44.8883	$44.89	$44.90	$44.90
Purchase #4	$93.70	11.831%	$104.7856	$104.79	$104.80	$104.80
Purchase #5	$145.30	3.437%	$150.294	$150.29	$150.30	$150.30
Purchase #6	$247.90	4.686%	$259.5166	$259.52	$259.50	$259.50
Purchase #7	$44.93	11.711%	$50.1918	$50.19	$50.20	$50.20
7 purchase totals =	$936.38		$1,002.5360	$1,002.54	$1,002.60	$1,002.60