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	$65.73	12.356%	$73.8516	$73.85	$73.85	$73.90
Purchase #2	$189.30	3.161%	$195.2838	$195.28	$195.30	$195.30
Purchase #3	$197.29	4.135%	$205.4479	$205.45	$205.45	$205.40
Purchase #4	$86.80	3.291%	$89.6566	$89.66	$89.65	$89.70
Purchase #5	$195.57	8.654%	$212.4946	$212.49	$212.50	$212.50
Purchase #6	$180.32	5.531%	$190.2935	$190.29	$190.30	$190.30
Purchase #7	$129.33	10.190%	$142.5087	$142.51	$142.50	$142.50
7 purchase totals =	$1,044.34		$1,109.5367	$1,109.53	$1,109.55	$1,109.60