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	$114.75	11.480%	$127.9233	$127.92	$127.90	$127.90
Purchase #2	$228.31	5.133%	$240.0292	$240.03	$240.05	$240.00
Purchase #3	$207.90	5.163%	$218.6339	$218.63	$218.65	$218.60
Purchase #4	$63.55	13.509%	$72.135	$72.14	$72.15	$72.10
Purchase #5	$30.49	6.797%	$32.5624	$32.56	$32.55	$32.60
Purchase #6	$184.62	4.705%	$193.3064	$193.31	$193.30	$193.30
Purchase #7	$214.85	13.222%	$243.2575	$243.26	$243.25	$243.30
7 purchase totals =	$1,044.47		$1,127.8477	$1,127.85	$1,127.85	$1,127.80