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	$128.46	13.352%	$145.612	$145.61	$145.60	$145.60
Purchase #2	$41.85	12.385%	$47.0331	$47.03	$47.05	$47.00
Purchase #3	$68.52	6.471%	$72.9539	$72.95	$72.95	$73.00
Purchase #4	$154.52	8.767%	$168.0668	$168.07	$168.05	$168.10
Purchase #5	$245.64	3.811%	$255.0013	$255.00	$255.00	$255.00
Purchase #6	$107.34	5.618%	$113.3704	$113.37	$113.35	$113.40
Purchase #7	$50.98	8.497%	$55.3118	$55.31	$55.30	$55.30
7 purchase totals =	$797.31		$857.3493	$857.34	$857.30	$857.40