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	$112.90	5.102%	$118.6602	$118.66	$118.65	$118.70
Purchase #2	$37.86	6.272%	$40.2346	$40.23	$40.25	$40.20
Purchase #3	$138.80	9.761%	$152.3483	$152.35	$152.35	$152.30
Purchase #4	$208.27	3.321%	$215.1866	$215.19	$215.20	$215.20
Purchase #5	$20.42	3.700%	$21.1755	$21.18	$21.20	$21.20
Purchase #6	$57.48	12.632%	$64.7409	$64.74	$64.75	$64.70
Purchase #7	$131.64	8.410%	$142.7109	$142.71	$142.70	$142.70
7 purchase totals =	$707.37		$755.0570	$755.06	$755.10	$755.00