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	$60.41	12.326%	$67.8561	$67.86	$67.85	$67.90
Purchase #2	$64.76	11.207%	$72.0177	$72.02	$72.00	$72.00
Purchase #3	$89.41	10.181%	$98.5128	$98.51	$98.50	$98.50
Purchase #4	$38.85	12.632%	$43.7575	$43.76	$43.75	$43.80
Purchase #5	$129.73	9.301%	$141.7962	$141.80	$141.80	$141.80
Purchase #6	$138.88	11.348%	$154.6401	$154.64	$154.65	$154.60
Purchase #7	$206.34	12.295%	$231.7095	$231.71	$231.70	$231.70
7 purchase totals =	$728.38		$810.2899	$810.30	$810.25	$810.30