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	$78.81	7.757%	$84.9233	$84.92	$84.90	$84.90
Purchase #2	$228.28	5.308%	$240.3971	$240.40	$240.40	$240.40
Purchase #3	$105.77	3.554%	$109.5291	$109.53	$109.55	$109.50
Purchase #4	$177.42	12.801%	$200.1315	$200.13	$200.15	$200.10
Purchase #5	$181.27	10.619%	$200.5191	$200.52	$200.50	$200.50
Purchase #6	$137.85	8.645%	$149.7671	$149.77	$149.75	$149.80
Purchase #7	$89.66	7.266%	$96.1747	$96.17	$96.15	$96.20
7 purchase totals =	$999.06		$1,081.4419	$1,081.44	$1,081.40	$1,081.40