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	$153.58	5.579%	$162.1482	$162.15	$162.15	$162.10
Purchase #2	$125.99	4.169%	$131.2425	$131.24	$131.25	$131.20
Purchase #3	$78.26	11.442%	$87.2145	$87.21	$87.20	$87.20
Purchase #4	$88.48	12.152%	$99.2321	$99.23	$99.25	$99.20
Purchase #5	$68.67	5.347%	$72.3418	$72.34	$72.35	$72.30
Purchase #6	$154.73	12.740%	$174.4426	$174.44	$174.45	$174.40
Purchase #7	$147.31	3.267%	$152.1226	$152.12	$152.10	$152.10
7 purchase totals =	$817.02		$878.7443	$878.73	$878.75	$878.50