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	$185.70	4.780%	$194.5765	$194.58	$194.60	$194.60
Purchase #2	$234.54	9.484%	$256.7838	$256.78	$256.80	$256.80
Purchase #3	$106.49	11.140%	$118.353	$118.35	$118.35	$118.40
Purchase #4	$151.48	11.535%	$168.9532	$168.95	$168.95	$169.00
Purchase #5	$156.73	11.400%	$174.5972	$174.60	$174.60	$174.60
Purchase #6	$226.89	8.389%	$245.9238	$245.92	$245.90	$245.90
Purchase #7	$49.29	11.332%	$54.8755	$54.88	$54.90	$54.90
7 purchase totals =	$1,111.12		$1,214.0630	$1,214.06	$1,214.10	$1,214.20