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	$124.37	13.623%	$141.3129	$141.31	$141.30	$141.30
Purchase #2	$64.75	11.219%	$72.0143	$72.01	$72.00	$72.00
Purchase #3	$55.89	7.516%	$60.0907	$60.09	$60.10	$60.10
Purchase #4	$12.37	9.346%	$13.5261	$13.53	$13.55	$13.50
Purchase #5	$128.27	7.501%	$137.8915	$137.89	$137.90	$137.90
Purchase #6	$247.69	10.401%	$273.4522	$273.45	$273.45	$273.50
Purchase #7	$32.94	9.162%	$35.958	$35.96	$35.95	$36.00
7 purchase totals =	$666.28		$734.2457	$734.24	$734.25	$734.30