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	$76.66	12.783%	$86.4594	$86.46	$86.45	$86.50
Purchase #2	$117.49	11.568%	$131.0812	$131.08	$131.10	$131.10
Purchase #3	$56.87	4.407%	$59.3763	$59.38	$59.40	$59.40
Purchase #4	$183.96	13.758%	$209.2692	$209.27	$209.25	$209.30
Purchase #5	$73.74	5.623%	$77.8864	$77.89	$77.90	$77.90
Purchase #6	$179.66	4.282%	$187.353	$187.35	$187.35	$187.40
Purchase #7	$94.90	7.353%	$101.878	$101.88	$101.90	$101.90
7 purchase totals =	$783.28		$853.3035	$853.31	$853.35	$853.50