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	$51.57	5.773%	$54.5471	$54.55	$54.55	$54.50
Purchase #2	$146.30	6.796%	$156.2425	$156.24	$156.25	$156.20
Purchase #3	$207.52	3.538%	$214.8621	$214.86	$214.85	$214.90
Purchase #4	$244.34	6.376%	$259.9191	$259.92	$259.90	$259.90
Purchase #5	$244.43	7.694%	$263.2364	$263.24	$263.25	$263.20
Purchase #6	$62.83	5.789%	$66.4672	$66.47	$66.45	$66.50
Purchase #7	$119.80	12.130%	$134.3317	$134.33	$134.35	$134.30
7 purchase totals =	$1,076.79		$1,149.6061	$1,149.61	$1,149.60	$1,149.50