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	$165.26	4.589%	$172.8438	$172.84	$172.85	$172.80
Purchase #2	$40.93	12.141%	$45.8993	$45.90	$45.90	$45.90
Purchase #3	$75.28	9.686%	$82.5716	$82.57	$82.55	$82.60
Purchase #4	$218.46	11.625%	$243.856	$243.86	$243.85	$243.90
Purchase #5	$181.42	3.397%	$187.5828	$187.58	$187.60	$187.60
Purchase #6	$119.46	11.519%	$133.2206	$133.22	$133.20	$133.20
Purchase #7	$7.47	10.364%	$8.2442	$8.24	$8.25	$8.20
7 purchase totals =	$808.28		$874.2183	$874.21	$874.20	$874.20