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	$144.53	4.572%	$151.1379	$151.14	$151.15	$151.10
Purchase #2	$158.47	8.418%	$171.81	$171.81	$171.80	$171.80
Purchase #3	$161.55	6.408%	$171.9021	$171.90	$171.90	$171.90
Purchase #4	$43.31	8.521%	$47.0004	$47.00	$47.00	$47.00
Purchase #5	$129.37	10.316%	$142.7158	$142.72	$142.70	$142.70
Purchase #6	$102.36	13.498%	$116.1766	$116.18	$116.20	$116.20
Purchase #7	$84.44	7.272%	$90.5805	$90.58	$90.60	$90.60
7 purchase totals =	$824.03		$891.3233	$891.33	$891.35	$891.30