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	$238.77	10.451%	$263.7239	$263.72	$263.70	$263.70
Purchase #2	$127.85	11.568%	$142.6397	$142.64	$142.65	$142.60
Purchase #3	$91.29	6.123%	$96.8797	$96.88	$96.90	$96.90
Purchase #4	$219.36	13.739%	$249.4979	$249.50	$249.50	$249.50
Purchase #5	$230.83	11.236%	$256.7661	$256.77	$256.75	$256.80
Purchase #6	$119.39	7.570%	$128.4278	$128.43	$128.45	$128.40
Purchase #7	$238.79	3.236%	$246.5172	$246.52	$246.50	$246.50
7 purchase totals =	$1,266.28		$1,384.4523	$1,384.46	$1,384.45	$1,384.40