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	$41.36	3.234%	$42.6976	$42.70	$42.70	$42.70
Purchase #2	$220.72	11.383%	$245.8446	$245.84	$245.85	$245.80
Purchase #3	$162.62	11.667%	$181.5929	$181.59	$181.60	$181.60
Purchase #4	$183.81	8.701%	$199.8033	$199.80	$199.80	$199.80
Purchase #5	$212.88	4.465%	$222.3851	$222.39	$222.40	$222.40
Purchase #6	$166.69	12.783%	$187.998	$188.00	$188.00	$188.00
Purchase #7	$96.59	9.625%	$105.8868	$105.89	$105.90	$105.90
7 purchase totals =	$1,084.67		$1,186.2083	$1,186.21	$1,186.25	$1,186.20