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	$54.30	9.429%	$59.4199	$59.42	$59.40	$59.40
Purchase #2	$112.28	12.632%	$126.4632	$126.46	$126.45	$126.50
Purchase #3	$84.78	13.561%	$96.277	$96.28	$96.30	$96.30
Purchase #4	$117.30	10.816%	$129.9872	$129.99	$130.00	$130.00
Purchase #5	$42.29	6.813%	$45.1712	$45.17	$45.15	$45.20
Purchase #6	$65.57	9.437%	$71.7578	$71.76	$71.75	$71.80
Purchase #7	$176.69	12.729%	$199.1809	$199.18	$199.20	$199.20
7 purchase totals =	$653.21		$728.2572	$728.26	$728.25	$728.40