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	$233.34	7.492%	$250.8218	$250.82	$250.80	$250.80
Purchase #2	$144.80	7.667%	$155.9018	$155.90	$155.90	$155.90
Purchase #3	$46.88	5.342%	$49.3843	$49.38	$49.40	$49.40
Purchase #4	$150.87	7.619%	$162.3648	$162.36	$162.35	$162.40
Purchase #5	$248.66	13.510%	$282.254	$282.25	$282.25	$282.30
Purchase #6	$249.74	5.430%	$263.3009	$263.30	$263.30	$263.30
Purchase #7	$87.81	13.233%	$99.4299	$99.43	$99.45	$99.40
7 purchase totals =	$1,162.10		$1,263.4575	$1,263.44	$1,263.45	$1,263.50