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	$80.28	8.585%	$87.172	$87.17	$87.15	$87.20
Purchase #2	$84.77	11.644%	$94.6406	$94.64	$94.65	$94.60
Purchase #3	$173.59	13.415%	$196.8771	$196.88	$196.90	$196.90
Purchase #4	$86.45	11.403%	$96.3079	$96.31	$96.30	$96.30
Purchase #5	$41.52	9.767%	$45.5753	$45.58	$45.60	$45.60
Purchase #6	$162.40	8.575%	$176.3258	$176.33	$176.35	$176.30
Purchase #7	$248.31	10.834%	$275.2119	$275.21	$275.20	$275.20
7 purchase totals =	$877.32		$972.1106	$972.12	$972.15	$972.10