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	$87.45	12.628%	$98.4932	$98.49	$98.50	$98.50
Purchase #2	$141.37	4.452%	$147.6638	$147.66	$147.65	$147.70
Purchase #3	$45.94	12.200%	$51.5447	$51.54	$51.55	$51.50
Purchase #4	$238.29	7.207%	$255.4636	$255.46	$255.45	$255.50
Purchase #5	$232.79	7.815%	$250.9825	$250.98	$251.00	$251.00
Purchase #6	$99.61	12.651%	$112.2117	$112.21	$112.20	$112.20
Purchase #7	$137.96	6.102%	$146.3783	$146.38	$146.40	$146.40
7 purchase totals =	$983.41		$1,062.7378	$1,062.72	$1,062.75	$1,062.80