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	$150.93	3.736%	$156.5687	$156.57	$156.55	$156.60
Purchase #2	$127.46	5.409%	$134.3543	$134.35	$134.35	$134.40
Purchase #3	$204.33	6.547%	$217.7075	$217.71	$217.70	$217.70
Purchase #4	$179.93	13.560%	$204.3285	$204.33	$204.35	$204.30
Purchase #5	$147.44	3.710%	$152.91	$152.91	$152.90	$152.90
Purchase #6	$64.53	12.382%	$72.5201	$72.52	$72.50	$72.50
Purchase #7	$135.82	12.309%	$152.5381	$152.54	$152.55	$152.50
7 purchase totals =	$1,010.44		$1,090.9272	$1,090.93	$1,090.90	$1,090.90