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	$95.49	13.168%	$108.0641	$108.06	$108.05	$108.10
Purchase #2	$95.80	5.148%	$100.7318	$100.73	$100.75	$100.70
Purchase #3	$244.45	11.663%	$272.9602	$272.96	$272.95	$273.00
Purchase #4	$148.75	5.419%	$156.8108	$156.81	$156.80	$156.80
Purchase #5	$9.93	13.663%	$11.2867	$11.29	$11.30	$11.30
Purchase #6	$12.75	12.312%	$14.3198	$14.32	$14.30	$14.30
Purchase #7	$99.37	10.554%	$109.8575	$109.86	$109.85	$109.90
7 purchase totals =	$706.54		$774.0309	$774.03	$774.00	$774.10