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	$176.82	4.565%	$184.8918	$184.89	$184.90	$184.90
Purchase #2	$203.98	5.658%	$215.5212	$215.52	$215.50	$215.50
Purchase #3	$196.79	4.345%	$205.3405	$205.34	$205.35	$205.30
Purchase #4	$175.40	12.331%	$197.0286	$197.03	$197.05	$197.00
Purchase #5	$145.71	11.340%	$162.2335	$162.23	$162.25	$162.20
Purchase #6	$30.63	9.730%	$33.6103	$33.61	$33.60	$33.60
Purchase #7	$23.98	13.865%	$27.3048	$27.30	$27.30	$27.30
7 purchase totals =	$953.31		$1,025.9307	$1,025.92	$1,025.95	$1,025.80