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	$118.87	7.215%	$127.4465	$127.45	$127.45	$127.40
Purchase #2	$74.32	11.451%	$82.8304	$82.83	$82.85	$82.80
Purchase #3	$250.61	5.199%	$263.6392	$263.64	$263.65	$263.60
Purchase #4	$73.25	12.498%	$82.4048	$82.40	$82.40	$82.40
Purchase #5	$21.38	9.322%	$23.373	$23.37	$23.35	$23.40
Purchase #6	$248.96	7.228%	$266.9548	$266.95	$266.95	$267.00
Purchase #7	$107.27	5.627%	$113.3061	$113.31	$113.30	$113.30
7 purchase totals =	$894.66		$959.9548	$959.95	$959.95	$959.90