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	$222.73	4.820%	$233.4656	$233.47	$233.45	$233.50
Purchase #2	$115.87	6.181%	$123.0319	$123.03	$123.05	$123.00
Purchase #3	$202.84	10.374%	$223.8826	$223.88	$223.90	$223.90
Purchase #4	$132.70	6.136%	$140.8425	$140.84	$140.85	$140.80
Purchase #5	$46.75	6.344%	$49.7158	$49.72	$49.70	$49.70
Purchase #6	$170.29	7.635%	$183.2916	$183.29	$183.30	$183.30
Purchase #7	$58.40	12.270%	$65.5657	$65.57	$65.55	$65.60
7 purchase totals =	$949.58		$1,019.7957	$1,019.80	$1,019.80	$1,019.80