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	$224.78	8.488%	$243.8593	$243.86	$243.85	$243.90
Purchase #2	$223.63	4.451%	$233.5838	$233.58	$233.60	$233.60
Purchase #3	$229.70	8.375%	$248.9374	$248.94	$248.95	$248.90
Purchase #4	$83.38	13.649%	$94.7605	$94.76	$94.75	$94.80
Purchase #5	$40.71	9.558%	$44.6011	$44.60	$44.60	$44.60
Purchase #6	$133.55	7.355%	$143.3726	$143.37	$143.35	$143.40
Purchase #7	$37.83	13.441%	$42.9147	$42.91	$42.90	$42.90
7 purchase totals =	$973.58		$1,052.0294	$1,052.02	$1,052.00	$1,052.10