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	$103.43	10.376%	$114.1619	$114.16	$114.15	$114.20
Purchase #2	$106.71	3.292%	$110.2229	$110.22	$110.20	$110.20
Purchase #3	$177.33	12.834%	$200.0885	$200.09	$200.10	$200.10
Purchase #4	$153.89	6.606%	$164.056	$164.06	$164.05	$164.10
Purchase #5	$51.37	5.361%	$54.1239	$54.12	$54.10	$54.10
Purchase #6	$39.56	7.616%	$42.5729	$42.57	$42.55	$42.60
Purchase #7	$176.93	7.738%	$190.6208	$190.62	$190.60	$190.60
7 purchase totals =	$809.22		$875.8469	$875.84	$875.75	$875.90