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	$106.73	4.718%	$111.7655	$111.77	$111.75	$111.80
Purchase #2	$70.77	8.289%	$76.6361	$76.64	$76.65	$76.60
Purchase #3	$136.81	3.349%	$141.3918	$141.39	$141.40	$141.40
Purchase #4	$135.74	11.690%	$151.608	$151.61	$151.60	$151.60
Purchase #5	$171.48	3.153%	$176.8868	$176.89	$176.90	$176.90
Purchase #6	$171.49	4.666%	$179.4917	$179.49	$179.50	$179.50
Purchase #7	$94.76	13.623%	$107.6692	$107.67	$107.65	$107.70
7 purchase totals =	$887.78		$945.4491	$945.46	$945.45	$945.50