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	$246.58	3.458%	$255.1067	$255.11	$255.10	$255.10
Purchase #2	$150.72	6.493%	$160.5062	$160.51	$160.50	$160.50
Purchase #3	$115.77	6.516%	$123.3136	$123.31	$123.30	$123.30
Purchase #4	$155.37	4.501%	$162.3632	$162.36	$162.35	$162.40
Purchase #5	$93.56	4.743%	$97.9976	$98.00	$98.00	$98.00
Purchase #6	$93.93	12.206%	$105.3951	$105.40	$105.40	$105.40
Purchase #7	$176.35	9.614%	$193.3043	$193.30	$193.30	$193.30
7 purchase totals =	$1,032.28		$1,097.9867	$1,097.99	$1,097.95	$1,098.00