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	$53.85	4.516%	$56.2819	$56.28	$56.30	$56.30
Purchase #2	$97.58	6.106%	$103.5382	$103.54	$103.55	$103.50
Purchase #3	$141.63	7.296%	$151.9633	$151.96	$151.95	$152.00
Purchase #4	$179.68	5.501%	$189.5642	$189.56	$189.55	$189.60
Purchase #5	$171.65	9.296%	$187.6066	$187.61	$187.60	$187.60
Purchase #6	$140.72	6.338%	$149.6388	$149.64	$149.65	$149.60
Purchase #7	$38.81	9.445%	$42.4756	$42.48	$42.50	$42.50
7 purchase totals =	$823.92		$881.0686	$881.07	$881.10	$881.10