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	$153.79	7.800%	$165.7856	$165.79	$165.80	$165.80
Purchase #2	$123.63	7.218%	$132.5536	$132.55	$132.55	$132.60
Purchase #3	$39.44	12.823%	$44.4974	$44.50	$44.50	$44.50
Purchase #4	$168.86	12.688%	$190.285	$190.29	$190.30	$190.30
Purchase #5	$200.46	3.529%	$207.5342	$207.53	$207.55	$207.50
Purchase #6	$104.34	13.612%	$118.5428	$118.54	$118.55	$118.50
Purchase #7	$170.89	11.768%	$191.0003	$191.00	$191.00	$191.00
7 purchase totals =	$961.41		$1,050.1989	$1,050.20	$1,050.25	$1,050.20