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	$177.64	12.423%	$199.7082	$199.71	$199.70	$199.70
Purchase #2	$191.89	8.686%	$208.5576	$208.56	$208.55	$208.60
Purchase #3	$28.36	9.326%	$31.0049	$31.00	$31.00	$31.00
Purchase #4	$127.44	11.532%	$142.1364	$142.14	$142.15	$142.10
Purchase #5	$87.80	3.510%	$90.8818	$90.88	$90.90	$90.90
Purchase #6	$183.57	3.147%	$189.3469	$189.35	$189.35	$189.30
Purchase #7	$151.39	3.561%	$156.781	$156.78	$156.80	$156.80
7 purchase totals =	$948.09		$1,018.4168	$1,018.42	$1,018.45	$1,018.40