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	$191.76	11.841%	$214.4663	$214.47	$214.45	$214.50
Purchase #2	$115.65	7.377%	$124.1815	$124.18	$124.20	$124.20
Purchase #3	$115.29	10.548%	$127.4508	$127.45	$127.45	$127.50
Purchase #4	$190.82	6.860%	$203.9103	$203.91	$203.90	$203.90
Purchase #5	$164.31	10.316%	$181.2602	$181.26	$181.25	$181.30
Purchase #6	$80.54	11.659%	$89.9302	$89.93	$89.95	$89.90
Purchase #7	$72.49	7.619%	$78.013	$78.01	$78.00	$78.00
7 purchase totals =	$930.86		$1,019.2123	$1,019.21	$1,019.20	$1,019.30