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	$168.31	8.321%	$182.3151	$182.32	$182.30	$182.30
Purchase #2	$84.73	8.472%	$91.9083	$91.91	$91.90	$91.90
Purchase #3	$170.25	5.133%	$178.9889	$178.99	$179.00	$179.00
Purchase #4	$128.78	8.225%	$139.3722	$139.37	$139.35	$139.40
Purchase #5	$46.75	12.219%	$52.4624	$52.46	$52.45	$52.50
Purchase #6	$177.40	10.785%	$196.5326	$196.53	$196.55	$196.50
Purchase #7	$206.51	13.604%	$234.6036	$234.60	$234.60	$234.60
7 purchase totals =	$982.73		$1,076.1831	$1,076.18	$1,076.15	$1,076.20