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	$79.51	3.199%	$82.0535	$82.05	$82.05	$82.10
Purchase #2	$158.25	10.581%	$174.9944	$174.99	$175.00	$175.00
Purchase #3	$73.47	8.771%	$79.9141	$79.91	$79.90	$79.90
Purchase #4	$76.30	3.260%	$78.7874	$78.79	$78.80	$78.80
Purchase #5	$79.81	12.482%	$89.7719	$89.77	$89.75	$89.80
Purchase #6	$91.59	8.151%	$99.0555	$99.06	$99.05	$99.10
Purchase #7	$126.66	10.223%	$139.6085	$139.61	$139.60	$139.60
7 purchase totals =	$685.59		$744.1853	$744.18	$744.15	$744.30