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	$167.72	12.196%	$188.1751	$188.18	$188.20	$188.20
Purchase #2	$27.53	5.617%	$29.0764	$29.08	$29.10	$29.10
Purchase #3	$23.27	6.397%	$24.7586	$24.76	$24.75	$24.80
Purchase #4	$156.80	7.454%	$168.4879	$168.49	$168.50	$168.50
Purchase #5	$37.53	13.396%	$42.5575	$42.56	$42.55	$42.60
Purchase #6	$181.85	11.532%	$202.8209	$202.82	$202.80	$202.80
Purchase #7	$178.77	6.780%	$190.8906	$190.89	$190.90	$190.90
7 purchase totals =	$773.47		$846.7670	$846.78	$846.80	$846.90