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	$91.59	3.577%	$94.8662	$94.87	$94.85	$94.90
Purchase #2	$106.49	7.172%	$114.1275	$114.13	$114.15	$114.10
Purchase #3	$102.82	5.526%	$108.5018	$108.50	$108.50	$108.50
Purchase #4	$197.91	12.438%	$222.526	$222.53	$222.55	$222.50
Purchase #5	$114.94	12.866%	$129.7282	$129.73	$129.75	$129.70
Purchase #6	$78.32	4.783%	$82.066	$82.07	$82.05	$82.10
Purchase #7	$187.97	11.501%	$209.5884	$209.59	$209.60	$209.60
7 purchase totals =	$880.04		$961.4041	$961.42	$961.45	$961.40