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	$41.33	12.573%	$46.5264	$46.53	$46.55	$46.50
Purchase #2	$153.85	4.261%	$160.4055	$160.41	$160.40	$160.40
Purchase #3	$82.69	13.462%	$93.8217	$93.82	$93.80	$93.80
Purchase #4	$29.54	6.705%	$31.5207	$31.52	$31.50	$31.50
Purchase #5	$222.83	9.350%	$243.6646	$243.66	$243.65	$243.70
Purchase #6	$162.57	7.817%	$175.2781	$175.28	$175.30	$175.30
Purchase #7	$51.57	7.170%	$55.2676	$55.27	$55.25	$55.30
7 purchase totals =	$744.38		$806.4846	$806.49	$806.45	$806.50