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	$181.44	7.222%	$194.5436	$194.54	$194.55	$194.50
Purchase #2	$81.92	4.244%	$85.3967	$85.40	$85.40	$85.40
Purchase #3	$169.96	9.623%	$186.3153	$186.32	$186.30	$186.30
Purchase #4	$161.54	4.146%	$168.2374	$168.24	$168.25	$168.20
Purchase #5	$97.77	11.190%	$108.7105	$108.71	$108.70	$108.70
Purchase #6	$225.48	3.847%	$234.1542	$234.15	$234.15	$234.20
Purchase #7	$204.78	6.854%	$218.8156	$218.82	$218.80	$218.80
7 purchase totals =	$1,122.89		$1,196.1733	$1,196.18	$1,196.15	$1,196.10