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	$93.96	6.620%	$100.1802	$100.18	$100.20	$100.20
Purchase #2	$94.45	11.865%	$105.6565	$105.66	$105.65	$105.70
Purchase #3	$48.72	10.709%	$53.9374	$53.94	$53.95	$53.90
Purchase #4	$41.75	13.371%	$47.3324	$47.33	$47.35	$47.30
Purchase #5	$41.37	5.214%	$43.527	$43.53	$43.55	$43.50
Purchase #6	$188.95	6.495%	$201.2223	$201.22	$201.20	$201.20
Purchase #7	$147.69	4.832%	$154.8264	$154.83	$154.85	$154.80
7 purchase totals =	$656.89		$706.6822	$706.69	$706.75	$706.60