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	$29.81	12.360%	$33.4945	$33.49	$33.50	$33.50
Purchase #2	$176.44	8.330%	$191.1375	$191.14	$191.15	$191.10
Purchase #3	$206.36	7.736%	$222.324	$222.32	$222.30	$222.30
Purchase #4	$201.73	11.852%	$225.639	$225.64	$225.65	$225.60
Purchase #5	$33.74	12.335%	$37.9018	$37.90	$37.90	$37.90
Purchase #6	$112.67	4.160%	$117.3571	$117.36	$117.35	$117.40
Purchase #7	$233.25	6.470%	$248.3413	$248.34	$248.35	$248.30
7 purchase totals =	$994.00		$1,076.1952	$1,076.19	$1,076.20	$1,076.10