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	$206.40	4.393%	$215.4672	$215.47	$215.45	$215.50
Purchase #2	$227.63	7.155%	$243.9169	$243.92	$243.90	$243.90
Purchase #3	$95.47	8.230%	$103.3272	$103.33	$103.35	$103.30
Purchase #4	$233.96	6.497%	$249.1604	$249.16	$249.15	$249.20
Purchase #5	$227.29	10.353%	$250.8213	$250.82	$250.80	$250.80
Purchase #6	$141.41	12.705%	$159.3761	$159.38	$159.40	$159.40
Purchase #7	$49.66	5.223%	$52.2537	$52.25	$52.25	$52.30
7 purchase totals =	$1,181.82		$1,274.3228	$1,274.33	$1,274.30	$1,274.40