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	$202.78	7.287%	$217.5566	$217.56	$217.55	$217.60
Purchase #2	$187.60	5.713%	$198.3176	$198.32	$198.30	$198.30
Purchase #3	$209.67	6.510%	$223.3195	$223.32	$223.30	$223.30
Purchase #4	$100.41	10.523%	$110.9761	$110.98	$111.00	$111.00
Purchase #5	$198.49	5.132%	$208.6765	$208.68	$208.70	$208.70
Purchase #6	$99.34	10.617%	$109.8869	$109.89	$109.90	$109.90
Purchase #7	$220.30	12.787%	$248.4698	$248.47	$248.45	$248.50
7 purchase totals =	$1,218.59		$1,317.2030	$1,317.22	$1,317.20	$1,317.30