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	$6.76	12.168%	$7.5826	$7.58	$7.60	$7.60
Purchase #2	$118.63	7.352%	$127.3517	$127.35	$127.35	$127.40
Purchase #3	$186.49	13.486%	$211.64	$211.64	$211.65	$211.60
Purchase #4	$134.54	4.835%	$141.045	$141.05	$141.05	$141.00
Purchase #5	$226.87	9.493%	$248.4068	$248.41	$248.40	$248.40
Purchase #6	$131.89	5.679%	$139.38	$139.38	$139.40	$139.40
Purchase #7	$202.51	3.805%	$210.2155	$210.22	$210.20	$210.20
7 purchase totals =	$1,007.69		$1,085.6216	$1,085.63	$1,085.65	$1,085.60