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	$212.34	8.433%	$230.2466	$230.25	$230.25	$230.20
Purchase #2	$79.81	3.201%	$82.3647	$82.36	$82.35	$82.40
Purchase #3	$102.71	7.799%	$110.7204	$110.72	$110.70	$110.70
Purchase #4	$82.64	8.615%	$89.7594	$89.76	$89.75	$89.80
Purchase #5	$26.46	3.726%	$27.4459	$27.45	$27.45	$27.40
Purchase #6	$180.35	4.176%	$187.8814	$187.88	$187.90	$187.90
Purchase #7	$91.31	8.865%	$99.4046	$99.40	$99.40	$99.40
7 purchase totals =	$775.62		$827.8230	$827.82	$827.80	$827.80