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	$59.67	12.739%	$67.2714	$67.27	$67.25	$67.30
Purchase #2	$165.72	11.625%	$184.985	$184.99	$185.00	$185.00
Purchase #3	$89.84	12.165%	$100.769	$100.77	$100.75	$100.80
Purchase #4	$145.95	12.860%	$164.7192	$164.72	$164.70	$164.70
Purchase #5	$145.34	10.372%	$160.4147	$160.41	$160.40	$160.40
Purchase #6	$198.88	6.376%	$211.5606	$211.56	$211.55	$211.60
Purchase #7	$149.31	12.326%	$167.714	$167.71	$167.70	$167.70
7 purchase totals =	$954.71		$1,057.4339	$1,057.43	$1,057.35	$1,057.50