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	$31.69	11.269%	$35.2611	$35.26	$35.25	$35.30
Purchase #2	$132.89	3.450%	$137.4747	$137.47	$137.45	$137.50
Purchase #3	$191.75	11.427%	$213.6613	$213.66	$213.65	$213.70
Purchase #4	$205.69	12.520%	$231.4424	$231.44	$231.45	$231.40
Purchase #5	$69.67	3.510%	$72.1154	$72.12	$72.10	$72.10
Purchase #6	$246.86	10.764%	$273.432	$273.43	$273.45	$273.40
Purchase #7	$141.96	10.159%	$156.3817	$156.38	$156.40	$156.40
7 purchase totals =	$1,020.51		$1,119.7686	$1,119.76	$1,119.75	$1,119.80