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	$191.68	4.607%	$200.5107	$200.51	$200.50	$200.50
Purchase #2	$50.82	5.262%	$53.4941	$53.49	$53.50	$53.50
Purchase #3	$70.77	10.745%	$78.3742	$78.37	$78.35	$78.40
Purchase #4	$202.48	8.829%	$220.357	$220.36	$220.35	$220.40
Purchase #5	$80.96	6.526%	$86.2434	$86.24	$86.25	$86.20
Purchase #6	$206.42	7.593%	$222.0935	$222.09	$222.10	$222.10
Purchase #7	$120.43	10.558%	$133.145	$133.15	$133.15	$133.10
7 purchase totals =	$923.56		$994.2179	$994.21	$994.20	$994.20