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	$42.62	8.684%	$46.3211	$46.32	$46.30	$46.30
Purchase #2	$59.72	6.751%	$63.7517	$63.75	$63.75	$63.80
Purchase #3	$127.40	11.277%	$141.7669	$141.77	$141.75	$141.80
Purchase #4	$188.66	3.816%	$195.8593	$195.86	$195.85	$195.90
Purchase #5	$115.51	11.311%	$128.5753	$128.58	$128.60	$128.60
Purchase #6	$198.89	7.735%	$214.2741	$214.27	$214.25	$214.30
Purchase #7	$246.53	5.217%	$259.3915	$259.39	$259.40	$259.40
7 purchase totals =	$979.33		$1,049.9399	$1,049.94	$1,049.90	$1,050.10