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	$222.99	4.777%	$233.6422	$233.64	$233.65	$233.60
Purchase #2	$181.35	7.367%	$194.7101	$194.71	$194.70	$194.70
Purchase #3	$193.32	11.763%	$216.0602	$216.06	$216.05	$216.10
Purchase #4	$239.67	9.760%	$263.0618	$263.06	$263.05	$263.10
Purchase #5	$63.47	13.655%	$72.1368	$72.14	$72.15	$72.10
Purchase #6	$231.36	13.623%	$262.8782	$262.88	$262.90	$262.90
Purchase #7	$69.79	3.697%	$72.3701	$72.37	$72.35	$72.40
7 purchase totals =	$1,201.95		$1,314.8594	$1,314.86	$1,314.85	$1,314.90