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	$31.96	4.579%	$33.4234	$33.42	$33.40	$33.40
Purchase #2	$243.71	4.626%	$254.984	$254.98	$255.00	$255.00
Purchase #3	$221.60	10.782%	$245.4929	$245.49	$245.50	$245.50
Purchase #4	$165.86	8.724%	$180.3296	$180.33	$180.35	$180.30
Purchase #5	$207.58	10.671%	$229.7309	$229.73	$229.75	$229.70
Purchase #6	$40.39	7.858%	$43.5638	$43.56	$43.55	$43.60
Purchase #7	$76.41	7.546%	$82.1759	$82.18	$82.20	$82.20
7 purchase totals =	$987.51		$1,069.7005	$1,069.69	$1,069.75	$1,069.70