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	$96.74	6.228%	$102.765	$102.77	$102.75	$102.80
Purchase #2	$77.50	7.477%	$83.2947	$83.29	$83.30	$83.30
Purchase #3	$174.43	7.136%	$186.8773	$186.88	$186.90	$186.90
Purchase #4	$214.86	7.315%	$230.577	$230.58	$230.60	$230.60
Purchase #5	$67.92	7.353%	$72.9142	$72.91	$72.90	$72.90
Purchase #6	$164.48	7.548%	$176.895	$176.90	$176.90	$176.90
Purchase #7	$243.58	4.808%	$255.2913	$255.29	$255.30	$255.30
7 purchase totals =	$1,039.51		$1,108.6145	$1,108.62	$1,108.65	$1,108.70