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	$127.63	11.470%	$142.2692	$142.27	$142.25	$142.30
Purchase #2	$78.87	13.541%	$89.5498	$89.55	$89.55	$89.50
Purchase #3	$113.42	12.604%	$127.7155	$127.72	$127.70	$127.70
Purchase #4	$177.86	8.545%	$193.0581	$193.06	$193.05	$193.10
Purchase #5	$50.93	12.782%	$57.4399	$57.44	$57.45	$57.40
Purchase #6	$96.33	11.147%	$107.0679	$107.07	$107.05	$107.10
Purchase #7	$79.59	8.573%	$86.4133	$86.41	$86.40	$86.40
7 purchase totals =	$724.63		$803.5137	$803.52	$803.45	$803.50