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	$145.66	7.229%	$156.1898	$156.19	$156.20	$156.20
Purchase #2	$147.87	13.562%	$167.9241	$167.92	$167.90	$167.90
Purchase #3	$168.76	6.757%	$180.1631	$180.16	$180.15	$180.20
Purchase #4	$171.31	10.509%	$189.313	$189.31	$189.30	$189.30
Purchase #5	$71.43	5.151%	$75.1094	$75.11	$75.10	$75.10
Purchase #6	$17.69	13.700%	$20.1135	$20.11	$20.10	$20.10
Purchase #7	$231.38	13.521%	$262.6649	$262.66	$262.65	$262.70
7 purchase totals =	$954.10		$1,051.4778	$1,051.46	$1,051.40	$1,051.50