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	$44.51	10.114%	$49.0117	$49.01	$49.00	$49.00
Purchase #2	$230.85	5.649%	$243.8907	$243.89	$243.90	$243.90
Purchase #3	$126.70	8.180%	$137.0641	$137.06	$137.05	$137.10
Purchase #4	$179.99	13.360%	$204.0367	$204.04	$204.05	$204.00
Purchase #5	$153.31	11.601%	$171.0955	$171.10	$171.10	$171.10
Purchase #6	$66.80	6.492%	$71.1367	$71.14	$71.15	$71.10
Purchase #7	$175.61	5.527%	$185.316	$185.32	$185.30	$185.30
7 purchase totals =	$977.77		$1,061.5514	$1,061.56	$1,061.55	$1,061.50