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	$175.34	7.517%	$188.5203	$188.52	$188.50	$188.50
Purchase #2	$119.66	3.494%	$123.8409	$123.84	$123.85	$123.80
Purchase #3	$174.64	13.839%	$198.8084	$198.81	$198.80	$198.80
Purchase #4	$19.64	6.340%	$20.8852	$20.89	$20.90	$20.90
Purchase #5	$145.98	11.108%	$162.1955	$162.20	$162.20	$162.20
Purchase #6	$167.43	8.585%	$181.8039	$181.80	$181.80	$181.80
Purchase #7	$133.54	9.425%	$146.1261	$146.13	$146.15	$146.10
7 purchase totals =	$936.23		$1,022.1803	$1,022.19	$1,022.20	$1,022.10