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	$29.91	10.477%	$33.0437	$33.04	$33.05	$33.00
Purchase #2	$207.59	5.663%	$219.3458	$219.35	$219.35	$219.30
Purchase #3	$74.54	5.642%	$78.7455	$78.75	$78.75	$78.70
Purchase #4	$114.41	8.580%	$124.2264	$124.23	$124.25	$124.20
Purchase #5	$200.98	7.168%	$215.3862	$215.39	$215.40	$215.40
Purchase #6	$227.73	11.242%	$253.3314	$253.33	$253.35	$253.30
Purchase #7	$119.52	7.528%	$128.5175	$128.52	$128.50	$128.50
7 purchase totals =	$974.68		$1,052.5965	$1,052.61	$1,052.65	$1,052.40