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	$25.46	7.479%	$27.3642	$27.36	$27.35	$27.40
Purchase #2	$6.27	13.372%	$7.1084	$7.11	$7.10	$7.10
Purchase #3	$231.37	3.142%	$238.6396	$238.64	$238.65	$238.60
Purchase #4	$249.43	10.376%	$275.3109	$275.31	$275.30	$275.30
Purchase #5	$151.88	5.736%	$160.5918	$160.59	$160.60	$160.60
Purchase #6	$89.62	11.478%	$99.9066	$99.91	$99.90	$99.90
Purchase #7	$232.38	11.683%	$259.529	$259.53	$259.55	$259.50
7 purchase totals =	$986.41		$1,068.4505	$1,068.45	$1,068.45	$1,068.40