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	$207.27	11.688%	$231.4957	$231.50	$231.50	$231.50
Purchase #2	$93.30	9.323%	$101.9984	$102.00	$102.00	$102.00
Purchase #3	$55.28	10.497%	$61.0827	$61.08	$61.10	$61.10
Purchase #4	$26.80	7.659%	$28.8526	$28.85	$28.85	$28.90
Purchase #5	$130.39	11.189%	$144.9793	$144.98	$145.00	$145.00
Purchase #6	$176.49	4.574%	$184.5627	$184.56	$184.55	$184.60
Purchase #7	$79.31	12.853%	$89.5037	$89.50	$89.50	$89.50
7 purchase totals =	$768.84		$842.4751	$842.47	$842.50	$842.60