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	$59.80	11.736%	$66.8181	$66.82	$66.80	$66.80
Purchase #2	$74.78	10.713%	$82.7912	$82.79	$82.80	$82.80
Purchase #3	$194.73	7.786%	$209.8917	$209.89	$209.90	$209.90
Purchase #4	$90.61	6.540%	$96.5359	$96.54	$96.55	$96.50
Purchase #5	$180.45	7.871%	$194.6532	$194.65	$194.65	$194.70
Purchase #6	$169.33	5.328%	$178.3519	$178.35	$178.35	$178.40
Purchase #7	$41.82	12.567%	$47.0755	$47.08	$47.10	$47.10
7 purchase totals =	$811.52		$876.1175	$876.12	$876.15	$876.20