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	$54.98	8.143%	$59.457	$59.46	$59.45	$59.50
Purchase #2	$114.39	7.796%	$123.3078	$123.31	$123.30	$123.30
Purchase #3	$60.73	9.362%	$66.4155	$66.42	$66.40	$66.40
Purchase #4	$202.95	8.557%	$220.3164	$220.32	$220.30	$220.30
Purchase #5	$206.56	6.782%	$220.5689	$220.57	$220.55	$220.60
Purchase #6	$148.63	8.677%	$161.5266	$161.53	$161.55	$161.50
Purchase #7	$152.83	10.133%	$168.3163	$168.32	$168.30	$168.30
7 purchase totals =	$941.07		$1,019.9085	$1,019.93	$1,019.85	$1,019.90