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	$82.52	12.204%	$92.5907	$92.59	$92.60	$92.60
Purchase #2	$234.88	3.405%	$242.8777	$242.88	$242.90	$242.90
Purchase #3	$145.80	5.844%	$154.3206	$154.32	$154.30	$154.30
Purchase #4	$191.28	10.236%	$210.8594	$210.86	$210.85	$210.90
Purchase #5	$244.96	9.872%	$269.1425	$269.14	$269.15	$269.10
Purchase #6	$206.78	8.285%	$223.9117	$223.91	$223.90	$223.90
Purchase #7	$228.31	13.321%	$258.7232	$258.72	$258.70	$258.70
7 purchase totals =	$1,334.53		$1,452.4258	$1,452.42	$1,452.40	$1,452.40