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	$141.37	7.643%	$152.1749	$152.17	$152.15	$152.20
Purchase #2	$115.51	13.397%	$130.9849	$130.98	$131.00	$131.00
Purchase #3	$163.79	9.146%	$178.7702	$178.77	$178.75	$178.80
Purchase #4	$132.88	8.614%	$144.3263	$144.33	$144.35	$144.30
Purchase #5	$154.34	3.713%	$160.0706	$160.07	$160.05	$160.10
Purchase #6	$136.92	11.450%	$152.5973	$152.60	$152.60	$152.60
Purchase #7	$249.73	5.718%	$264.0096	$264.01	$264.00	$264.00
7 purchase totals =	$1,094.54		$1,182.9338	$1,182.93	$1,182.90	$1,183.00