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	$208.66	4.794%	$218.6632	$218.66	$218.65	$218.70
Purchase #2	$72.26	10.740%	$80.0207	$80.02	$80.00	$80.00
Purchase #3	$123.88	12.270%	$139.0801	$139.08	$139.10	$139.10
Purchase #4	$65.43	9.551%	$71.6792	$71.68	$71.70	$71.70
Purchase #5	$188.34	4.261%	$196.3652	$196.37	$196.35	$196.40
Purchase #6	$184.50	10.712%	$204.2636	$204.26	$204.25	$204.30
Purchase #7	$82.97	11.596%	$92.5912	$92.59	$92.60	$92.60
7 purchase totals =	$926.04		$1,002.6632	$1,002.66	$1,002.65	$1,002.80