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	$161.95	6.817%	$172.9901	$172.99	$173.00	$173.00
Purchase #2	$79.27	12.590%	$89.2501	$89.25	$89.25	$89.30
Purchase #3	$242.59	4.335%	$253.1063	$253.11	$253.10	$253.10
Purchase #4	$99.30	13.697%	$112.9011	$112.90	$112.90	$112.90
Purchase #5	$200.64	6.791%	$214.2655	$214.27	$214.25	$214.30
Purchase #6	$74.86	9.611%	$82.0548	$82.05	$82.05	$82.10
Purchase #7	$182.35	5.663%	$192.6765	$192.68	$192.70	$192.70
7 purchase totals =	$1,040.96		$1,117.2444	$1,117.25	$1,117.25	$1,117.40