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	$155.76	8.221%	$168.565	$168.57	$168.55	$168.60
Purchase #2	$80.47	11.268%	$89.5374	$89.54	$89.55	$89.50
Purchase #3	$120.84	8.575%	$131.202	$131.20	$131.20	$131.20
Purchase #4	$243.82	10.761%	$270.0575	$270.06	$270.05	$270.10
Purchase #5	$179.40	8.472%	$194.5988	$194.60	$194.60	$194.60
Purchase #6	$220.64	8.130%	$238.578	$238.58	$238.60	$238.60
Purchase #7	$66.51	13.254%	$75.3252	$75.33	$75.35	$75.30
7 purchase totals =	$1,067.44		$1,167.8639	$1,167.88	$1,167.90	$1,167.90