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	$47.59	9.288%	$52.0102	$52.01	$52.00	$52.00
Purchase #2	$74.62	5.402%	$78.651	$78.65	$78.65	$78.70
Purchase #3	$17.89	5.333%	$18.8441	$18.84	$18.85	$18.80
Purchase #4	$127.41	9.655%	$139.7114	$139.71	$139.70	$139.70
Purchase #5	$205.34	10.118%	$226.1163	$226.12	$226.10	$226.10
Purchase #6	$26.73	13.836%	$30.4284	$30.43	$30.45	$30.40
Purchase #7	$56.97	13.791%	$64.8267	$64.83	$64.85	$64.80
7 purchase totals =	$556.55		$610.5881	$610.59	$610.60	$610.50