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	$175.33	5.852%	$185.5903	$185.59	$185.60	$185.60
Purchase #2	$91.64	10.108%	$100.903	$100.90	$100.90	$100.90
Purchase #3	$53.33	4.218%	$55.5795	$55.58	$55.60	$55.60
Purchase #4	$87.27	9.492%	$95.5537	$95.55	$95.55	$95.60
Purchase #5	$103.97	10.254%	$114.6311	$114.63	$114.65	$114.60
Purchase #6	$62.81	8.749%	$68.3052	$68.31	$68.30	$68.30
Purchase #7	$211.50	6.399%	$225.0339	$225.03	$225.05	$225.00
7 purchase totals =	$785.85		$845.5967	$845.59	$845.65	$845.60