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	$182.92	3.360%	$189.0661	$189.07	$189.05	$189.10
Purchase #2	$105.63	5.166%	$111.0868	$111.09	$111.10	$111.10
Purchase #3	$58.35	10.618%	$64.5456	$64.55	$64.55	$64.50
Purchase #4	$176.72	6.486%	$188.1821	$188.18	$188.20	$188.20
Purchase #5	$181.94	7.605%	$195.7765	$195.78	$195.80	$195.80
Purchase #6	$123.30	3.239%	$127.2937	$127.29	$127.30	$127.30
Purchase #7	$187.82	8.605%	$203.9819	$203.98	$204.00	$204.00
7 purchase totals =	$1,016.68		$1,079.9327	$1,079.94	$1,080.00	$1,080.00