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	$43.67	6.411%	$46.4697	$46.47	$46.45	$46.50
Purchase #2	$149.58	9.829%	$164.2822	$164.28	$164.30	$164.30
Purchase #3	$219.50	9.331%	$239.9815	$239.98	$240.00	$240.00
Purchase #4	$141.70	6.209%	$150.4982	$150.50	$150.50	$150.50
Purchase #5	$24.25	4.393%	$25.3153	$25.32	$25.30	$25.30
Purchase #6	$170.52	13.474%	$193.4959	$193.50	$193.50	$193.50
Purchase #7	$51.50	6.405%	$54.7986	$54.80	$54.80	$54.80
7 purchase totals =	$800.72		$874.8414	$874.85	$874.85	$874.90