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	$234.87	13.396%	$266.3332	$266.33	$266.35	$266.30
Purchase #2	$82.94	7.447%	$89.1165	$89.12	$89.10	$89.10
Purchase #3	$39.58	5.741%	$41.8523	$41.85	$41.85	$41.90
Purchase #4	$193.47	3.435%	$200.1157	$200.12	$200.10	$200.10
Purchase #5	$35.89	8.726%	$39.0218	$39.02	$39.00	$39.00
Purchase #6	$249.40	9.654%	$273.4771	$273.48	$273.50	$273.50
Purchase #7	$179.93	4.647%	$188.2913	$188.29	$188.30	$188.30
7 purchase totals =	$1,016.08		$1,098.2079	$1,098.21	$1,098.20	$1,098.20