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	$116.92	8.643%	$127.0254	$127.03	$127.05	$127.00
Purchase #2	$141.72	6.364%	$150.7391	$150.74	$150.75	$150.70
Purchase #3	$205.98	12.283%	$231.2805	$231.28	$231.30	$231.30
Purchase #4	$151.34	4.323%	$157.8824	$157.88	$157.90	$157.90
Purchase #5	$93.47	13.274%	$105.8772	$105.88	$105.90	$105.90
Purchase #6	$224.35	11.542%	$250.2445	$250.24	$250.25	$250.20
Purchase #7	$47.49	8.481%	$51.5176	$51.52	$51.50	$51.50
7 purchase totals =	$981.27		$1,074.5667	$1,074.57	$1,074.65	$1,074.50