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	$204.84	8.536%	$222.3251	$222.33	$222.35	$222.30
Purchase #2	$91.38	3.302%	$94.3974	$94.40	$94.40	$94.40
Purchase #3	$110.92	6.651%	$118.2973	$118.30	$118.30	$118.30
Purchase #4	$131.75	4.648%	$137.8737	$137.87	$137.85	$137.90
Purchase #5	$211.50	8.361%	$229.1835	$229.18	$229.20	$229.20
Purchase #6	$81.28	11.298%	$90.463	$90.46	$90.45	$90.50
Purchase #7	$69.25	4.858%	$72.6142	$72.61	$72.60	$72.60
7 purchase totals =	$900.92		$965.1542	$965.15	$965.15	$965.20