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	$30.41	3.707%	$31.5373	$31.54	$31.55	$31.50
Purchase #2	$32.92	13.397%	$37.3303	$37.33	$37.35	$37.30
Purchase #3	$52.99	12.525%	$59.627	$59.63	$59.65	$59.60
Purchase #4	$128.33	9.188%	$140.121	$140.12	$140.10	$140.10
Purchase #5	$194.69	9.203%	$212.6073	$212.61	$212.60	$212.60
Purchase #6	$68.83	4.695%	$72.0616	$72.06	$72.05	$72.10
Purchase #7	$197.96	11.331%	$220.3908	$220.39	$220.40	$220.40
7 purchase totals =	$706.13		$773.6753	$773.68	$773.70	$773.60