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	$183.41	8.734%	$199.429	$199.43	$199.45	$199.40
Purchase #2	$54.60	3.554%	$56.5405	$56.54	$56.55	$56.50
Purchase #3	$176.34	11.284%	$196.2382	$196.24	$196.25	$196.20
Purchase #4	$30.55	8.774%	$33.2305	$33.23	$33.25	$33.20
Purchase #5	$55.50	11.607%	$61.9419	$61.94	$61.95	$61.90
Purchase #6	$112.61	6.786%	$120.2517	$120.25	$120.25	$120.30
Purchase #7	$7.45	8.130%	$8.0557	$8.06	$8.05	$8.10
7 purchase totals =	$620.46		$675.6875	$675.69	$675.75	$675.60