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	$101.80	12.199%	$114.2186	$114.22	$114.20	$114.20
Purchase #2	$225.97	12.633%	$254.5168	$254.52	$254.50	$254.50
Purchase #3	$13.61	7.578%	$14.6414	$14.64	$14.65	$14.60
Purchase #4	$124.52	11.751%	$139.1523	$139.15	$139.15	$139.20
Purchase #5	$156.59	3.361%	$161.853	$161.85	$161.85	$161.90
Purchase #6	$116.75	8.815%	$127.0415	$127.04	$127.05	$127.00
Purchase #7	$183.36	3.656%	$190.0636	$190.06	$190.05	$190.10
7 purchase totals =	$922.60		$1,001.4872	$1,001.48	$1,001.45	$1,001.50