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	$187.62	12.404%	$210.8924	$210.89	$210.90	$210.90
Purchase #2	$246.41	5.351%	$259.5954	$259.60	$259.60	$259.60
Purchase #3	$92.93	11.163%	$103.3038	$103.30	$103.30	$103.30
Purchase #4	$133.62	11.478%	$148.9569	$148.96	$148.95	$149.00
Purchase #5	$55.52	3.207%	$57.3005	$57.30	$57.30	$57.30
Purchase #6	$231.42	11.607%	$258.2809	$258.28	$258.30	$258.30
Purchase #7	$58.39	7.214%	$62.6023	$62.60	$62.60	$62.60
7 purchase totals =	$1,005.91		$1,100.9322	$1,100.93	$1,100.95	$1,101.00