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	$175.96	12.806%	$198.4934	$198.49	$198.50	$198.50
Purchase #2	$189.44	3.840%	$196.7145	$196.71	$196.70	$196.70
Purchase #3	$78.57	6.829%	$83.9355	$83.94	$83.95	$83.90
Purchase #4	$28.95	12.737%	$32.6374	$32.64	$32.65	$32.60
Purchase #5	$73.44	5.585%	$77.5416	$77.54	$77.55	$77.50
Purchase #6	$250.64	3.301%	$258.9136	$258.91	$258.90	$258.90
Purchase #7	$162.42	12.384%	$182.5341	$182.53	$182.55	$182.50
7 purchase totals =	$959.42		$1,030.7701	$1,030.76	$1,030.80	$1,030.60