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	$50.35	4.169%	$52.4491	$52.45	$52.45	$52.40
Purchase #2	$62.47	7.152%	$66.9379	$66.94	$66.95	$66.90
Purchase #3	$132.69	3.459%	$137.2797	$137.28	$137.30	$137.30
Purchase #4	$171.66	6.175%	$182.26	$182.26	$182.25	$182.30
Purchase #5	$37.54	9.588%	$41.1393	$41.14	$41.15	$41.10
Purchase #6	$180.61	7.665%	$194.4538	$194.45	$194.45	$194.50
Purchase #7	$179.86	4.159%	$187.3404	$187.34	$187.35	$187.30
7 purchase totals =	$815.18		$861.8602	$861.86	$861.90	$861.80