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	$134.63	9.629%	$147.5935	$147.59	$147.60	$147.60
Purchase #2	$212.60	10.404%	$234.7189	$234.72	$234.70	$234.70
Purchase #3	$35.89	3.651%	$37.2003	$37.20	$37.20	$37.20
Purchase #4	$89.46	3.418%	$92.5177	$92.52	$92.50	$92.50
Purchase #5	$201.83	7.216%	$216.3941	$216.39	$216.40	$216.40
Purchase #6	$94.87	4.712%	$99.3403	$99.34	$99.35	$99.30
Purchase #7	$238.93	9.835%	$262.4288	$262.43	$262.45	$262.40
7 purchase totals =	$1,008.21		$1,090.1936	$1,090.19	$1,090.20	$1,090.10