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	$9.43	8.681%	$10.2486	$10.25	$10.25	$10.20
Purchase #2	$12.27	6.658%	$13.0869	$13.09	$13.10	$13.10
Purchase #3	$208.83	9.318%	$228.2888	$228.29	$228.30	$228.30
Purchase #4	$82.43	8.277%	$89.2527	$89.25	$89.25	$89.30
Purchase #5	$74.79	7.160%	$80.145	$80.15	$80.15	$80.10
Purchase #6	$53.54	3.798%	$55.5734	$55.57	$55.55	$55.60
Purchase #7	$6.92	5.832%	$7.3236	$7.32	$7.30	$7.30
7 purchase totals =	$448.21		$483.9190	$483.92	$483.90	$483.90