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	$47.44	8.370%	$51.4107	$51.41	$51.40	$51.40
Purchase #2	$144.54	5.702%	$152.7817	$152.78	$152.80	$152.80
Purchase #3	$64.26	9.574%	$70.4123	$70.41	$70.40	$70.40
Purchase #4	$119.80	10.484%	$132.3598	$132.36	$132.35	$132.40
Purchase #5	$234.46	8.697%	$254.851	$254.85	$254.85	$254.90
Purchase #6	$181.51	8.261%	$196.5045	$196.50	$196.50	$196.50
Purchase #7	$167.72	12.551%	$188.7705	$188.77	$188.75	$188.80
7 purchase totals =	$959.73		$1,047.0905	$1,047.08	$1,047.05	$1,047.20