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	$109.36	4.135%	$113.882	$113.88	$113.90	$113.90
Purchase #2	$177.33	4.396%	$185.1254	$185.13	$185.15	$185.10
Purchase #3	$73.32	13.641%	$83.3216	$83.32	$83.30	$83.30
Purchase #4	$11.96	4.333%	$12.4782	$12.48	$12.50	$12.50
Purchase #5	$239.55	6.618%	$255.4034	$255.40	$255.40	$255.40
Purchase #6	$158.28	6.399%	$168.4083	$168.41	$168.40	$168.40
Purchase #7	$64.45	9.308%	$70.449	$70.45	$70.45	$70.40
7 purchase totals =	$834.25		$889.0679	$889.07	$889.10	$889.00