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	$229.95	5.679%	$243.0089	$243.01	$243.00	$243.00
Purchase #2	$124.94	3.645%	$129.4941	$129.49	$129.50	$129.50
Purchase #3	$73.76	11.369%	$82.1458	$82.15	$82.15	$82.10
Purchase #4	$134.93	11.621%	$150.6102	$150.61	$150.60	$150.60
Purchase #5	$107.91	3.823%	$112.0354	$112.04	$112.05	$112.00
Purchase #6	$85.54	4.298%	$89.2165	$89.22	$89.20	$89.20
Purchase #7	$215.89	12.466%	$242.8028	$242.80	$242.80	$242.80
7 purchase totals =	$972.92		$1,049.3137	$1,049.32	$1,049.30	$1,049.20