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	$98.31	10.837%	$108.9639	$108.96	$108.95	$109.00
Purchase #2	$180.25	4.601%	$188.5433	$188.54	$188.55	$188.50
Purchase #3	$148.33	13.346%	$168.1261	$168.13	$168.15	$168.10
Purchase #4	$110.60	7.386%	$118.7689	$118.77	$118.75	$118.80
Purchase #5	$119.31	3.538%	$123.5312	$123.53	$123.55	$123.50
Purchase #6	$59.82	5.203%	$62.9324	$62.93	$62.95	$62.90
Purchase #7	$236.43	5.717%	$249.9467	$249.95	$249.95	$249.90
7 purchase totals =	$953.05		$1,020.8125	$1,020.81	$1,020.85	$1,020.70