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	$71.83	9.338%	$78.5375	$78.54	$78.55	$78.50
Purchase #2	$13.59	12.817%	$15.3318	$15.33	$15.35	$15.30
Purchase #3	$23.77	4.333%	$24.8	$24.80	$24.80	$24.80
Purchase #4	$33.26	6.121%	$35.2958	$35.30	$35.30	$35.30
Purchase #5	$144.46	12.468%	$162.4713	$162.47	$162.45	$162.50
Purchase #6	$122.83	11.163%	$136.5415	$136.54	$136.55	$136.50
Purchase #7	$225.69	12.257%	$253.3528	$253.35	$253.35	$253.40
7 purchase totals =	$635.43		$706.3307	$706.33	$706.35	$706.30